pgsql_fdw, FDW for PostgreSQL server

diff --git a/contrib/Makefile b/contrib/Makefile
index 0c238aa..e09e61e 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...a2b88ec .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,504 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 	PGconn		   *conn = NULL;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/* Is there any cached and valid connection with such key? */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (found)
+ 	{
+ 		if (entry->conn != NULL)
+ 		{
+ 			entry->refs++;
+ 			elog(DEBUG1,
+ 				 "reuse connection %u/%u (%d)",
+ 				 entry->serverid,
+ 				 entry->userid,
+ 				 entry->refs);
+ 			return entry->conn;
+ 		}
+ 
+ 		/*
+ 		 * Connection cache entry was found but connection in it is invalid.
+ 		 * We reuse entry to store newly established connection later.
+ 		 */
+ 	}
+ 	else
+ 	{
+ 		/*
+ 		 * Use ResourceOwner to clean the connection up on error including
+ 		 * user interrupt.
+ 		 */
+ 		elog(DEBUG1,
+ 			 "create entry for %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * Here we have to establish new connection.
+ 	 * Use PG_TRY block to ensure closing connection on error.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		/* Connect to the foreign PostgreSQL server */
+ 		conn = connect_pg_server(server, user);
+ 
+ 		/*
+ 		 * Initialize the cache entry to keep new connection.
+ 		 * Note: key items of entry has been initialized in
+ 		 * hash_search(HASH_ENTER).
+ 		 */
+ 		entry->refs = 1;
+ 		entry->conn = conn;
+ 		elog(DEBUG1,
+ 			 "connected to %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQfinish(conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	/*
+ 	 * Start transaction to use cursor to retrieve data separately.
+ 	 */
+ 	res = PQexec(conn, "BEGIN");
+ 	if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		elog(ERROR, "could not start transaction");
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If the caller was the last referrer, unregister it from cache.
+ 	 * TODO: Note that sharing connections requires a mechanism to detect
+ 	 * change of FDW object to invalidate lasting connections.
+ 	 */
+ 	entry->refs--;
+ 	elog(DEBUG1,
+ 		 "connection %u/%u released (%d)",
+ 		 entry->serverid,
+ 		 entry->userid,
+ 		 entry->refs);
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		elog(DEBUG1,
+ 			 "closing connection %u/%u",
+ 			 entry->serverid,
+ 			 entry->userid);
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ 	else
+ 		elog(DEBUG1,
+ 			 "connection %u/%u already closed",
+ 			 entry->serverid,
+ 			 entry->userid);
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			elog(DEBUG1, "found: %u/%u", entry->serverid, entry->userid);
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 	elog(DEBUG1, "closed connection %u/%u", serverid, userid);
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...694534f .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...c1c74ac .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,377 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_proc_remotely_executable(Oid procid);
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
+  * If they are safe to be evaluated on the remote side.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which qual can be pushed down.
+ 	 *
+ 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
+ 	 * clause of result SQL string, and they could be removed from PlanState
+ 	 * to avoid duplicate evaluation at ExecScan().
+ 	 *
+ 	 * We never change the quals in the Plan node, because this execution might
+ 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
+ 	 * reused to construct another PlanState for subsequent EXECUTE statement.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 		List	   *local_qual = NIL;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 
+ 			/* Determine whether the qual can be pushed down or not. */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 			else
+ 			{
+ 				List	   *attrs;
+ 
+ 				/*
+ 				 * We need to know which attributes are used in qual evaluated
+ 				 * on the local server, because they should be listed in the
+ 				 * SELECT clause of remote query.  We can ignore attributes
+ 				 * which are referenced only in ORDER BY/GROUP BY clause because
+ 				 * such attributes has already been kept in reltargetlist.
+ 				 */
+ 				attrs = pull_var_clause((Node *) ri->clause,
+ 										PVC_RECURSE_AGGREGATES,
+ 										PVC_RECURSE_PLACEHOLDERS);
+ 				attr_used = list_union(attr_used, attrs);
+ 
+ 				/*
+ 				 * Save the RestrictInfo to replace baserel->baserestrictinfo
+ 				 * afterward.
+ 				 */
+ 				local_qual = lappend(local_qual, ri);
+ 			}
+ 		}
+ 
+ 		/*
+ 		 * Remove quals which are going to evaluated on the foreign server to
+ 		 * avoid overhead of duplicated evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(relid, InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(relid, InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname;
+ 
+ 				/* Ignore droppped attributes. */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					continue;
+ 
+ 				colname = GetFdwOptionValue(relid, attr, "colname");
+ 				if (colname == NULL)
+ 					colname = strVal(list_nth(rte->eref->colnames, attr - 1));
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore droppped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_ArrayExpr:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtre of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Operators which use non-immutable function can't be pushed down.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_proc_remotely_executable(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_FuncExpr:
+ 			/*
+ 			 * Non-immutable functions can't be pushed down.
+ 			 */
+ 			{
+ 				FuncExpr   *fe = (FuncExpr *) node;
+ 
+ 				if (!is_proc_remotely_executable(fe->funcid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if func is known as safe to be pushed down if all of the
+  * arguments are also known as safe.
+  */
+ static bool
+ is_proc_remotely_executable(Oid procid)
+ {
+ 	/*
+ 	 * User-defined procedures can't be pushed down.
+ 	 */
+ 	if (procid >= FirstNormalObjectId)
+ 		return false;
+ 
+ 	return true;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...514e759 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,408 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERRROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, min_cursor_rows, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD min_cursor_rows '0');
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', min_cursor_rows '10', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft1 OPTIONS (min_cursor_rows 'a');          -- ERROR
+ ERROR:  invalid value for min_cursor_rows: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (min_cursor_rows '-1');         -- ERROR
+ ERROR:  invalid value for min_cursor_rows: "-1"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', min_cursor_rows '0', fetch_count '2')                                                                                                                                                                                                                                                                                 | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                                List of foreign tables
+  Schema | Table |  Server   |                               FDW Options                               | Description 
+ --------+-------+-----------+-------------------------------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                                          | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', min_cursor_rows '10', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                QUERY PLAN                                
+ -------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5
+    ->  Sort
+          Output: c1, c2, c3, c4, c5
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5
+                Remote SQL: SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                QUERY PLAN                                
+ -------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5
+    ->  Sort
+          Output: c1, c2, c3, c4, c5
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5
+                Remote SQL: SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ -- with WHERE clause
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            
+ ------+----+-------+------------------------------+--------------------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                         QUERY PLAN                                         
+ -------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Remote SQL: SELECT NULL, NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+    ->  Foreign Scan on ft2 t2
+          Remote SQL: SELECT NULL, NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
+ (5 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Nested Loop
+          Join Filter: (t1.c3 = t2.c3)
+          ->  HashAggregate
+                ->  Foreign Scan on ft2 t2
+                      Filter: (date_part('dow'::text, c4) = 6::double precision)
+                      Remote SQL: DECLARE pgsql_fdw_cursor_6 SCROLL CURSOR FOR SELECT NULL, NULL, c3, c4, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
+          ->  Foreign Scan on ft1 t1
+                Remote SQL: SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
+ (10 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                               QUERY PLAN                                                                               
+ -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Remote SQL: SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Remote SQL: SELECT NULL, NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" > 10) AND (date_part('dow'::text, c5) = 6::double precision)) 
+ (10 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970
+ (1 row)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...a62b2ab .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,270 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by smaller objects.
+ 	 */
+ 	{"min_cursor_rows", ForeignTableRelationId, false},
+ 	{"min_cursor_rows", ForeignServerRelationId, false},
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* min_cursor_rows be zero or positive digit number. */
+ 		if (strcmp(def->defname, "min_cursor_rows") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 0)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check if the provided option is one of the valid options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	/*
+ 	 * If the option was other than libpq option, look up option table and
+ 	 * determine valid context.
+ 	 */
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check if the provided option is one of the valid options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	/*
+ 	 * If the option was other than libpq option, look up option table and
+ 	 * determine valid context.
+ 	 */
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...87dfa29 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,36 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...e9dfa74 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,882 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "optimizer/cost.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor mode.  This can be override by fetch_count
+  * FDW option.
+  */
+ #define DEFAULT_FETCH_COUNT			1000
+ 
+ /*
+  * Default minimum estimated row count for cursor mode.  This can be override
+  * by min_cursor_rows FDW option.
+  * */
+ #define DEFAULT_MIN_CURSOR_ROWS		1000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 
+ 	/* Items for cursor mode */
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * This macro can be used in the executor to determine whether the scan is
+  * using CURSOR or not.
+  */
+ #define USE_CURSOR(fdwplan)	\
+ 	(list_length((fdwplan)->fdw_private) > FdwPrivateDeclareSql)
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan, partial in cursor mode */
+ 	bool		cursor_opened;	/* true if cursor is opened */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	FdwRoutine *fdwroutine = makeNode(FdwRoutine);
+ 
+ 	fdwroutine->PlanForeignScan = pgsqlPlanForeignScan;
+ 	fdwroutine->ExplainForeignScan = pgsqlExplainForeignScan;
+ 	fdwroutine->BeginForeignScan = pgsqlBeginForeignScan;
+ 	fdwroutine->IterateForeignScan = pgsqlIterateForeignScan;
+ 	fdwroutine->ReScanForeignScan = pgsqlReScanForeignScan;
+ 	fdwroutine->EndForeignScan = pgsqlEndForeignScan;
+ 
+ 	PG_RETURN_POINTER(fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char	   *sql;
+ 	FdwPlan	   *fdwplan;
+ 	List	   *fdw_private = NIL;
+ 	const char *min_cursor_rows_str;
+ 	int	min_cursor_rows = DEFAULT_MIN_CURSOR_ROWS;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/*
+ 	 * We use SQL-level cursor when the result seems to be large, to limit
+ 	 * memory usage for the result set. Exceptionally we use simple SELECT if
+ 	 * min_cursor_rows is set to 0.
+ 	 */
+ 	min_cursor_rows_str = GetFdwOptionValue(foreigntableid,
+ 											InvalidAttrNumber,
+ 											"min_cursor_rows");
+ 	if (min_cursor_rows_str != NULL)
+ 		min_cursor_rows = strtol(min_cursor_rows_str, NULL, 10);
+ 
+ 	if (min_cursor_rows != 0 && baserel->rows >= min_cursor_rows)
+ 	{
+ 		char			name[128];	/* must be larger than format + 10 */
+ 		StringInfoData	cursor;
+ 		const char	   *fetch_count_str;
+ 		int				fetch_count = DEFAULT_FETCH_COUNT;
+ 
+ 		/* Use specified fetch_count instead of default value, if any. */
+ 		fetch_count_str = GetFdwOptionValue(foreigntableid,
+ 											InvalidAttrNumber,
+ 											"fetch_count");
+ 		if (fetch_count_str != NULL)
+ 			fetch_count = strtol(fetch_count_str, NULL, 10);
+ 		elog(DEBUG1,
+ 			 "relid=%u fetch_count=%d",
+ 			 foreigntableid,
+ 			 fetch_count);
+ 
+ 		/* We store some more information in FdwPlan to pass them beyond the
+ 		 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 		 * would hold items below:
+ 		 *
+ 		 * 1) plain SELECT statement (already added above)
+ 		 * 2) SQL statement used to declare cursor
+ 		 * 3) SQL statement used to fetch rows from cursor
+ 		 * 4) SQL statement used to reset cursor 
+ 		 * 5) SQL statement used to close cursor
+ 		 *
+ 		 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 		 * can be accessed directly via list_nth().  For example of FETCH
+ 		 * statement:
+ 		 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 		 */
+ 
+ 		/* Construct cursor name from sequential value */
+ 		sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 		/* Construct statement to declare cursor */
+ 		initStringInfo(&cursor);
+ 		appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 		fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 		/* Construct statement to fetch rows from cursor */
+ 		initStringInfo(&cursor);
+ 		appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 		fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 		/* Construct statement to reset cursor */
+ 		initStringInfo(&cursor);
+ 		appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 		fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 		/* Construct statement to close cursor */
+ 		initStringInfo(&cursor);
+ 		appendStringInfo(&cursor, "CLOSE %s", name);
+ 		fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 	}
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	if (USE_CURSOR(fdwplan))
+ 		sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	else
+ 		sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateSelectSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 	festate->cursor_opened = false;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL && !festate->cursor_opened)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* If the scan doesn't use cursor, the scan has been done. */
+ 	if (!USE_CURSOR(festate->fdwplan))
+ 	{
+ 		ExecClearTuple(slot);
+ 		return slot;
+ 	}
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Discard fetch results if any. */
+ 	if (festate->tuples != NULL)
+ 	{
+ 		tuplestore_end(festate->tuples);
+ 		festate->tuples = NULL;
+ 	}
+ 
+ 	/* Reset cursor */
+ 	if (USE_CURSOR(festate->fdwplan))
+ 	{
+ 		fdw_private = festate->fdwplan->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		PG_TRY();
+ 		{
+ 			if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 			{
+ 				ereport(ERROR,
+ 						(errmsg("could not rewind cursor"),
+ 						 errdetail("%s", PQerrorMessage(conn)),
+ 						 errhint("%s", sql)));
+ 			}
+ 			PQclear(res);
+ 			res = NULL;
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			PQclear(res);
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	if (festate->tuples != NULL)
+ 	{
+ 		tuplestore_end(festate->tuples);
+ 		festate->tuples = NULL;
+ 	}
+ 
+ 	/* Close cursor */
+ 	if (USE_CURSOR(festate->fdwplan) && festate->cursor_opened)
+ 	{
+ 		fdw_private = festate->fdwplan->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		PG_TRY();
+ 		{
+ 			if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 			{
+ 				ereport(ERROR,
+ 						(errmsg("could not close cursor"),
+ 						 errdetail("%s", PQerrorMessage(conn)),
+ 						 errhint("%s", sql)));
+ 			}
+ 			PQclear(res);
+ 			res = NULL;
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			PQclear(res);
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	ReleaseConnection(festate->conn);
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	char		   *endp;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN (FORMAT YAML) %s", sql);
+ 
+ 	/* remove WHERE clause if the query uses parameter */
+ 	p = strchr(buf.data, '$');
+ 	if (p != NULL)
+ 	{
+ 		p = strstr(buf.data, "WHERE");
+ 		if (p != NULL)
+ 			*p = '\0';
+ 	}
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			PQclear(res);
+ 			res = NULL;
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 		plan = pstrdup(PQgetvalue(res, 0, 0));
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/* extract startup cost from remote plan */
+ 	p = strstr(plan, "Startup Cost: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Startup Cost: ");
+ 		*startup_cost = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for startup cost%c", *endp);
+ 	}
+ 
+ 	/* extract total cost from remote plan */
+ 	p = strstr(plan, "Total Cost: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Total Cost: ");
+ 		*total_cost = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for total cost");
+ 	}
+ 
+ 	/* extract # of rows from remote plan */
+ 	p = strstr(plan, "Plan Rows: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Plan Rows: ");
+ 		baserel->rows = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for plan rows");
+ 	}
+ 
+ 	/* extract average width from remote plan */
+ 	p = strstr(plan, "Plan Width: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Plan Width: ");
+ 		baserel->width = strtol(p, &endp, 10);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for plan width");
+ 	}
+ 
+ 	/* TODO Selectivity of quals pushed down should be considered. */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	int				required_result;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	if (USE_CURSOR(fdwplan))
+ 	{
+ 		sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 		required_result = PGRES_COMMAND_OK;
+ 	}
+ 	else
+ 	{
+ 		sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateSelectSql));
+ 		required_result = PGRES_TUPLES_OK;
+ 	}
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (res == NULL || PQresultStatus(res) != required_result)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not execute foreign query"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Fetch first bunch of result if we using cursor. */
+ 		if (USE_CURSOR(fdwplan))
+ 		{
+ 			/* Mark that this scan has opened a cursor. */
+ 			festate->cursor_opened = true;
+ 
+ 			/* Discard result of CURSOR statement and fetch first bunch. */
+ 			PQclear(res);
+ 			res = fetch_result(node);
+ 		}
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(MessageContext);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...fb49ffb .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...c00de92 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,177 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERRROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD min_cursor_rows '0');
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', min_cursor_rows '10', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft1 OPTIONS (min_cursor_rows 'a');          -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (min_cursor_rows '-1');         -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101;
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index adf09ca..65c7e81 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index ed39e0b..d72590f 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 123,128 ****
--- 123,129 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...dd2d711 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,271 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   The <application>pgsql_fdw</application> can be installed on only
+   <productname>PostgreSQL</productname> 9.1 or later, but it can also access
+   data stored in <productname>PostgreSQL</productname> 9.0.
+   <productname>PostgreSQL</productname>8.4 or older are not available as remote
+   server because <application>pgsql_fdw</application> uses YAML format of
+   <command>EXPLAIN</command> output.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> switches the way used to retrieve
+     result of remote query according to estimated number of result rows.
+     If the estimation was less than a threshold, the result rows are retrieved
+     at once with simple <command>SELECT</command> statement.
+     In contrast, if the estimation is larger than the threshold, the result
+     rows are fetched separately with a cursor defined by
+     <command>DECLARE</command> statement.
+    </para>
+ 
+    <para>
+     Users can control this behavior with setting cursor options for a foreign
+     table.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>min_cursor_rows</literal></term>
+      <listitem>
+       <para>
+        This option specifies the minimum estimated number of result rows to use
+        cursor for fetching result.  Setting this to 1 means that every query
+        uses cursor, and setting to 0 means that every query uses simple
+        <command>SELECT</command>.  This option can be set on a foreign table,
+        and accepts only positive integer value.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows fetched at once in cursor mode.
+        This option accepts only integer value larger than zero.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until locla role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> executes <command>BEGIN</command>
+    command when a new connection has established.  This means that all remote
+    queries for a foreign server are executed in a transaction.  Since the
+    default transaction isolation level is <literal>READ COMMITTED</literal>,
+    multiple foreign scans in a local query might produce inconsistent results.
+ 
+    To avoid this inconsistency, you can use <literal>SERIALIZABLE</literal>
+    level for remote transaction with setting
+    <literal>default_transaction_isolation</literal> for the user used for
+    <application>pgsql_fdw</application> connection on remote side.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding some basic costs:  connection costs, remote query costs and
+    data transfer costs.
+    To get remote query costs <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+ 
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                           QUERY PLAN
+ -----------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8769.00 rows=1 width=4)
+    Remote SQL: SELECT aid, NULL, NULL, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
+ (2 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 75923a6..6fda053 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a single relation
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 8a1c82e..a56366f 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 626,631 ****
--- 626,632 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/Makefile b/contrib/Makefile
index 0c238aa..e09e61e 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...a2b88ec .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,504 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 	PGconn		   *conn = NULL;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/* Is there any cached and valid connection with such key? */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (found)
+ 	{
+ 		if (entry->conn != NULL)
+ 		{
+ 			entry->refs++;
+ 			elog(DEBUG1,
+ 				 "reuse connection %u/%u (%d)",
+ 				 entry->serverid,
+ 				 entry->userid,
+ 				 entry->refs);
+ 			return entry->conn;
+ 		}
+ 
+ 		/*
+ 		 * Connection cache entry was found but connection in it is invalid.
+ 		 * We reuse entry to store newly established connection later.
+ 		 */
+ 	}
+ 	else
+ 	{
+ 		/*
+ 		 * Use ResourceOwner to clean the connection up on error including
+ 		 * user interrupt.
+ 		 */
+ 		elog(DEBUG1,
+ 			 "create entry for %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * Here we have to establish new connection.
+ 	 * Use PG_TRY block to ensure closing connection on error.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		/* Connect to the foreign PostgreSQL server */
+ 		conn = connect_pg_server(server, user);
+ 
+ 		/*
+ 		 * Initialize the cache entry to keep new connection.
+ 		 * Note: key items of entry has been initialized in
+ 		 * hash_search(HASH_ENTER).
+ 		 */
+ 		entry->refs = 1;
+ 		entry->conn = conn;
+ 		elog(DEBUG1,
+ 			 "connected to %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQfinish(conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	/*
+ 	 * Start transaction to use cursor to retrieve data separately.
+ 	 */
+ 	res = PQexec(conn, "BEGIN");
+ 	if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		elog(ERROR, "could not start transaction");
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If the caller was the last referrer, unregister it from cache.
+ 	 * TODO: Note that sharing connections requires a mechanism to detect
+ 	 * change of FDW object to invalidate lasting connections.
+ 	 */
+ 	entry->refs--;
+ 	elog(DEBUG1,
+ 		 "connection %u/%u released (%d)",
+ 		 entry->serverid,
+ 		 entry->userid,
+ 		 entry->refs);
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		elog(DEBUG1,
+ 			 "closing connection %u/%u",
+ 			 entry->serverid,
+ 			 entry->userid);
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ 	else
+ 		elog(DEBUG1,
+ 			 "connection %u/%u already closed",
+ 			 entry->serverid,
+ 			 entry->userid);
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			elog(DEBUG1, "found: %u/%u", entry->serverid, entry->userid);
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 	elog(DEBUG1, "closed connection %u/%u", serverid, userid);
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...694534f .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...c1c74ac .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,377 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_proc_remotely_executable(Oid procid);
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
+  * If they are safe to be evaluated on the remote side.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which qual can be pushed down.
+ 	 *
+ 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
+ 	 * clause of result SQL string, and they could be removed from PlanState
+ 	 * to avoid duplicate evaluation at ExecScan().
+ 	 *
+ 	 * We never change the quals in the Plan node, because this execution might
+ 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
+ 	 * reused to construct another PlanState for subsequent EXECUTE statement.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 		List	   *local_qual = NIL;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 
+ 			/* Determine whether the qual can be pushed down or not. */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 			else
+ 			{
+ 				List	   *attrs;
+ 
+ 				/*
+ 				 * We need to know which attributes are used in qual evaluated
+ 				 * on the local server, because they should be listed in the
+ 				 * SELECT clause of remote query.  We can ignore attributes
+ 				 * which are referenced only in ORDER BY/GROUP BY clause because
+ 				 * such attributes has already been kept in reltargetlist.
+ 				 */
+ 				attrs = pull_var_clause((Node *) ri->clause,
+ 										PVC_RECURSE_AGGREGATES,
+ 										PVC_RECURSE_PLACEHOLDERS);
+ 				attr_used = list_union(attr_used, attrs);
+ 
+ 				/*
+ 				 * Save the RestrictInfo to replace baserel->baserestrictinfo
+ 				 * afterward.
+ 				 */
+ 				local_qual = lappend(local_qual, ri);
+ 			}
+ 		}
+ 
+ 		/*
+ 		 * Remove quals which are going to evaluated on the foreign server to
+ 		 * avoid overhead of duplicated evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(relid, InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(relid, InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname;
+ 
+ 				/* Ignore droppped attributes. */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					continue;
+ 
+ 				colname = GetFdwOptionValue(relid, attr, "colname");
+ 				if (colname == NULL)
+ 					colname = strVal(list_nth(rte->eref->colnames, attr - 1));
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore droppped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_ArrayExpr:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtre of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Operators which use non-immutable function can't be pushed down.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_proc_remotely_executable(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_FuncExpr:
+ 			/*
+ 			 * Non-immutable functions can't be pushed down.
+ 			 */
+ 			{
+ 				FuncExpr   *fe = (FuncExpr *) node;
+ 
+ 				if (!is_proc_remotely_executable(fe->funcid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if func is known as safe to be pushed down if all of the
+  * arguments are also known as safe.
+  */
+ static bool
+ is_proc_remotely_executable(Oid procid)
+ {
+ 	/*
+ 	 * User-defined procedures can't be pushed down.
+ 	 */
+ 	if (procid >= FirstNormalObjectId)
+ 		return false;
+ 
+ 	return true;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...e913892 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,406 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERRROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                       QUERY PLAN                                                      
+ ----------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5
+    ->  Sort
+          Output: c1, c2, c3, c4, c5
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                       QUERY PLAN                                                      
+ ----------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5
+    ->  Sort
+          Output: c1, c2, c3, c4, c5
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ -- with WHERE clause
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            
+ ------+----+-------+------------------------------+--------------------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Remote SQL: DECLARE pgsql_fdw_cursor_17 SCROLL CURSOR FOR SELECT NULL, NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+    ->  Foreign Scan on ft2 t2
+          Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT NULL, NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
+ (5 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                      QUERY PLAN                                                                     
+ ----------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Nested Loop
+          Join Filter: (t1.c3 = t2.c3)
+          ->  HashAggregate
+                ->  Foreign Scan on ft2 t2
+                      Filter: (date_part('dow'::text, c4) = 6::double precision)
+                      Remote SQL: DECLARE pgsql_fdw_cursor_24 SCROLL CURSOR FOR SELECT NULL, NULL, c3, c4, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
+          ->  Foreign Scan on ft1 t1
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
+ (10 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                                                      QUERY PLAN                                                                                                      
+ ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Remote SQL: DECLARE pgsql_fdw_cursor_30 SCROLL CURSOR FOR SELECT NULL, NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" > 10) AND (date_part('dow'::text, c5) = 6::double precision)) 
+ (10 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970
+ (1 row)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...5eac503 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,254 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check if the provided option is one of the valid options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	/*
+ 	 * If the option was other than libpq option, look up option table and
+ 	 * determine valid context.
+ 	 */
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check if the provided option is one of the valid options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	/*
+ 	 * If the option was other than libpq option, look up option table and
+ 	 * determine valid context.
+ 	 */
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...87dfa29 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,36 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...18a6d85 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,811 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "optimizer/cost.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overrideen by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			1000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ 	bool		cursor_opened;	/* true if cursor has benn opened */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	FdwRoutine *fdwroutine = makeNode(FdwRoutine);
+ 
+ 	fdwroutine->PlanForeignScan = pgsqlPlanForeignScan;
+ 	fdwroutine->ExplainForeignScan = pgsqlExplainForeignScan;
+ 	fdwroutine->BeginForeignScan = pgsqlBeginForeignScan;
+ 	fdwroutine->IterateForeignScan = pgsqlIterateForeignScan;
+ 	fdwroutine->ReScanForeignScan = pgsqlReScanForeignScan;
+ 	fdwroutine->EndForeignScan = pgsqlEndForeignScan;
+ 
+ 	PG_RETURN_POINTER(fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(foreigntableid,
+ 										InvalidAttrNumber,
+ 										"fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1,
+ 		 "relid=%u fetch_count=%d",
+ 		 foreigntableid,
+ 		 fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 	festate->cursor_opened = false;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL && !festate->cursor_opened)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (!festate->cursor_opened)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	if (festate->tuples != NULL)
+ 		tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	if (festate->tuples != NULL)
+ 	{
+ 		tuplestore_end(festate->tuples);
+ 		festate->tuples = NULL;
+ 	}
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	char		   *endp;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN (FORMAT YAML) %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 		plan = pstrdup(PQgetvalue(res, 0, 0));
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/* extract startup cost from remote plan */
+ 	p = strstr(plan, "Startup Cost: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Startup Cost: ");
+ 		*startup_cost = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for startup cost%c", *endp);
+ 	}
+ 
+ 	/* extract total cost from remote plan */
+ 	p = strstr(plan, "Total Cost: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Total Cost: ");
+ 		*total_cost = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for total cost");
+ 	}
+ 
+ 	/* extract # of rows from remote plan */
+ 	p = strstr(plan, "Plan Rows: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Plan Rows: ");
+ 		baserel->rows = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for plan rows");
+ 	}
+ 
+ 	/* extract average width from remote plan */
+ 	p = strstr(plan, "Plan Width: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Plan Width: ");
+ 		baserel->width = strtol(p, &endp, 10);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for plan width");
+ 	}
+ 
+ 	/* TODO Selectivity of quals pushed down should be considered. */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (res == NULL || PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Mark that this scan has opened a cursor. */
+ 		festate->cursor_opened = true;
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(MessageContext);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...fb49ffb .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...3db9606 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,175 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERRROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101;
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index adf09ca..65c7e81 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index ed39e0b..d72590f 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 123,128 ****
--- 123,129 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...f594ed8 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,251 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   The <application>pgsql_fdw</application> can be installed on only
+   <productname>PostgreSQL</productname> 9.1 or later, but it can also access
+   data stored in <productname>PostgreSQL</productname> 9.0.
+   <productname>PostgreSQL</productname>8.4 or older are not available as remote
+   server because <application>pgsql_fdw</application> uses YAML format of
+   <command>EXPLAIN</command> output.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until locla role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> executes <command>BEGIN</command>
+    command when a new connection has established.  This means that all remote
+    queries for a foreign server are executed in a transaction.  Since the
+    default transaction isolation level is <literal>READ COMMITTED</literal>,
+    multiple foreign scans in a local query might produce inconsistent results.
+ 
+    To avoid this inconsistency, you can use <literal>SERIALIZABLE</literal>
+    level for remote transaction with setting
+    <literal>default_transaction_isolation</literal> for the user used for
+    <application>pgsql_fdw</application> connection on remote side.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding some basic costs:  connection costs, remote query costs and
+    data transfer costs.
+    To get remote query costs <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+ 
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                           QUERY PLAN
+ -----------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8769.00 rows=1 width=4)
+    Remote SQL: SELECT aid, NULL, NULL, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
+ (2 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 75923a6..6fda053 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a single relation
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 8a1c82e..a56366f 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 626,631 ****
--- 626,632 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 1cf3b3c..4a7ffa6 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 26,32 ****
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 26,32 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 345,398 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 345,373 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..d809cac 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 235,238 ****
--- 235,392 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum, const char *optname);
+ </programlisting>
+ 
+      This function returns a copied string (created in current memory context)
+      of the value of a FDW option with given name which is set on a object with
+      given oid and attribute number.  This function ignores catalogs if invalid
+      identifir is given for it.
+ 
+      <itemizedlist>
+       <listitem>
+        <para>
+         If attnum is <literal>InvalidAttrNumber</literal> or relid is
+         <literal>Invalidoid</literal>, <structname>pg_attribute</structname> is
+         ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If relid is <literal>InvalidOid</literal>,
+         <structname>pg_foreign_table</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If both serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_server</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If all of fdwid, serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_data_wrapper</structname> is ignored.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+ 
+     <para>
+      If the option with given name is set in multiple object level, the one in
+      the finest-grained object is used; e.g. priority is given to user mappings 
+      over than foreign servers.
+      This function would be useful when you know which option is needed but you
+      don't know where it is set.  If you already know the source object, it
+      would be more efficient to use object retrieval functions.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index a7d30a1..b984a5e 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
*************** GetForeignTable(Oid relid)
*** 248,253 ****
--- 248,378 ----
  
  
  /*
+  * If an option entry which matches the given name was found in the given
+  * list, returns a copy of arg string, otherwise returns NULL.
+  */
+ static char *
+ get_options_value(List *options, const char *optname)
+ {
+ 	ListCell   *lc;
+ 
+ 	/* Find target option from the list. */
+ 	foreach (lc, options)
+ 	{
+ 		DefElem	   *def = lfirst(lc);
+ 
+ 		if (strcmp(def->defname, optname) == 0)
+ 			return pstrdup(strVal(def->arg));
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ /*
+  * Returns a copy of the value of specified option with searching the option
+  * from appropriate catalog.  If an option was stored in multiple object
+  * levels, one in the finest-grained object level is used; lookup order is:
+  *   1) pg_attribute (only when both attnum and relid are valid)
+  *   2) pg_foreign_table (only when relid is valid)
+  *   3) pg_user_mapping (only when serverid or relid is valid)
+  *   4) pg_foreign_server (only when serverid or relid is valid)
+  *   5) pg_foreign_data_wrapper (only when fdwid or serverid or relid is valid)
+  * This priority rule would be useful in most cases using FDW options.
+  *
+  * If attnum was InvalidAttrNumber, we don't retrieve FDW optiosn from
+  * pg_attribute.attfdwoptions.
+  */
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum,
+ 				  const char *optname)
+ {
+ 	ForeignTable   *table = NULL;
+ 	UserMapping	   *user = NULL;
+ 	ForeignServer  *server = NULL;
+ 	ForeignDataWrapper  *wrapper = NULL;
+ 	char		   *value;
+ 
+ 	/* Do we need to search pg_attribute? */
+ 	if (attnum != InvalidAttrNumber && relid != InvalidOid)
+ 	{
+ 		value = get_options_value(GetForeignColumnOptions(relid, attnum),
+ 								  optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_table? */
+ 	if (relid != InvalidOid)
+ 	{
+ 		table = GetForeignTable(relid);
+ 		value = get_options_value(table->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		serverid = table->serverid;
+ 	}
+ 
+ 	/* Do we need to search pg_user_mapping and pg_foreign_server? */
+ 	if (serverid != InvalidOid)
+ 	{
+ 		user = GetUserMapping(GetOuterUserId(), serverid);
+ 		value = get_options_value(user->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		server = GetForeignServer(serverid);
+ 		value = get_options_value(server->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		fdwid = server->fdwid;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_data_wrapper? */
+ 	if (fdwid != InvalidOid)
+ 	{
+ 		wrapper = GetForeignDataWrapper(fdwid);
+ 		value = get_options_value(wrapper->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ 
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
+ 
+ /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
   * to get its FdwRoutine struct.
   */
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 2c436ae..6498162 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,83 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern char *GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid,
+ 							AttrNumber attnum, const char *optname);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/Makefile b/contrib/Makefile
index 0c238aa..e09e61e 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...b497dab .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,508 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 	PGconn		   *conn = NULL;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/* Is there any cached and valid connection with such key? */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (found)
+ 	{
+ 		if (entry->conn != NULL)
+ 		{
+ 			entry->refs++;
+ 			elog(DEBUG1,
+ 				 "reuse connection %u/%u (%d)",
+ 				 entry->serverid,
+ 				 entry->userid,
+ 				 entry->refs);
+ 			return entry->conn;
+ 		}
+ 
+ 		/*
+ 		 * Connection cache entry was found but connection in it is invalid.
+ 		 * We reuse entry to store newly established connection later.
+ 		 */
+ 	}
+ 	else
+ 	{
+ 		/*
+ 		 * Use ResourceOwner to clean the connection up on error including
+ 		 * user interrupt.
+ 		 */
+ 		elog(DEBUG1,
+ 			 "create entry for %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * Here we have to establish new connection.
+ 	 * Use PG_TRY block to ensure closing connection on error.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		/* Connect to the foreign PostgreSQL server */
+ 		conn = connect_pg_server(server, user);
+ 
+ 		/*
+ 		 * Initialize the cache entry to keep new connection.
+ 		 * Note: key items of entry has been initialized in
+ 		 * hash_search(HASH_ENTER).
+ 		 */
+ 		entry->refs = 1;
+ 		entry->conn = conn;
+ 		elog(DEBUG1,
+ 			 "connected to %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQfinish(conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	/*
+ 	 * Start transaction to use cursor to retrieve data separately.
+ 	 */
+ 	res = PQexec(conn, "BEGIN");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction");
+ 	}
+ 	PQclear(res);
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If the caller was the last referrer, unregister it from cache.
+ 	 * TODO: Note that sharing connections requires a mechanism to detect
+ 	 * change of FDW object to invalidate lasting connections.
+ 	 */
+ 	entry->refs--;
+ 	elog(DEBUG1,
+ 		 "connection %u/%u released (%d)",
+ 		 entry->serverid,
+ 		 entry->userid,
+ 		 entry->refs);
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		elog(DEBUG1,
+ 			 "closing connection %u/%u",
+ 			 entry->serverid,
+ 			 entry->userid);
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ 	else
+ 		elog(DEBUG1,
+ 			 "connection %u/%u already closed",
+ 			 entry->serverid,
+ 			 entry->userid);
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			elog(DEBUG1, "found: %u/%u", entry->serverid, entry->userid);
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 	elog(DEBUG1, "closed connection %u/%u", serverid, userid);
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...694534f .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...b5f6c79 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,364 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_proc_remotely_executable(Oid procid);
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
+  * If they are safe to be evaluated on the remote side.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which qual can be pushed down.
+ 	 *
+ 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
+ 	 * clause of result SQL string, and they could be removed from PlanState
+ 	 * to avoid duplicate evaluation at ExecScan().
+ 	 *
+ 	 * We never change the quals in the Plan node, because this execution might
+ 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
+ 	 * reused to construct another PlanState for subsequent EXECUTE statement.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/* Determine whether the qual can be pushed down or not. */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname;
+ 
+ 				/* Ignore dropped attributes. */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					continue;
+ 
+ 				colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 											attr, "colname");
+ 				if (colname == NULL)
+ 					colname = strVal(list_nth(rte->eref->colnames, attr - 1));
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_ArrayExpr:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Operators which use non-immutable function can't be pushed down.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_proc_remotely_executable(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_FuncExpr:
+ 			/*
+ 			 * Non-immutable functions can't be pushed down.
+ 			 */
+ 			{
+ 				FuncExpr   *fe = (FuncExpr *) node;
+ 
+ 				if (!is_proc_remotely_executable(fe->funcid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if func is known as safe to be pushed down if all of the
+  * arguments are also known as safe.
+  */
+ static bool
+ is_proc_remotely_executable(Oid procid)
+ {
+ 	/*
+ 	 * User-defined procedures can't be pushed down.
+ 	 */
+ 	if (procid >= FirstNormalObjectId)
+ 		return false;
+ 
+ 	return true;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...a26c775 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,462 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                       QUERY PLAN                                                      
+ ----------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5
+    ->  Sort
+          Output: c1, c2, c3, c4, c5
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                       QUERY PLAN                                                      
+ ----------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5
+    ->  Sort
+          Output: c1, c2, c3, c4, c5
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ -- with WHERE clause
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101;
+  c1  | c2 |  c3   |              c4              |            c5            
+ -----+----+-------+------------------------------+--------------------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            
+ ------+----+-------+------------------------------+--------------------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                 QUERY PLAN                                                                
+ ------------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_17 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+    ->  Foreign Scan on ft2 t2
+          Filter: (c1 = 2)
+          Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
+ (7 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                      QUERY PLAN                                                                      
+ -----------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Nested Loop
+          Join Filter: (t1.c3 = t2.c3)
+          ->  HashAggregate
+                ->  Foreign Scan on ft2 t2
+                      Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                      Remote SQL: DECLARE pgsql_fdw_cursor_24 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
+ (11 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                                                      QUERY PLAN                                                                                                     
+ --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_30 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5 FROM "S 1"."T 1" WHERE (("C 1" > 10) AND (date_part('dow'::text, c5) = 6::double precision)) 
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            
+ ----+----+-------+------------------------------+--------------------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_36 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_37 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_38 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_39 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...e123cba .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...61d20ee .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,871 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ 	bool		cursor_opened;	/* true if cursor has been opened */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	FdwRoutine *fdwroutine = makeNode(FdwRoutine);
+ 
+ 	fdwroutine->PlanForeignScan = pgsqlPlanForeignScan;
+ 	fdwroutine->ExplainForeignScan = pgsqlExplainForeignScan;
+ 	fdwroutine->BeginForeignScan = pgsqlBeginForeignScan;
+ 	fdwroutine->IterateForeignScan = pgsqlIterateForeignScan;
+ 	fdwroutine->ReScanForeignScan = pgsqlReScanForeignScan;
+ 	fdwroutine->EndForeignScan = pgsqlEndForeignScan;
+ 
+ 	PG_RETURN_POINTER(fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 	festate->cursor_opened = false;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL && !festate->cursor_opened)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (!festate->cursor_opened)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	if (festate->tuples != NULL)
+ 		tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (!festate->cursor_opened)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	if (festate->tuples != NULL)
+ 	{
+ 		tuplestore_end(festate->tuples);
+ 		festate->tuples = NULL;
+ 	}
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	char		   *endp;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* goundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN (FORMAT YAML) %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 		plan = pstrdup(PQgetvalue(res, 0, 0));
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/* extract startup cost from remote plan */
+ 	p = strstr(plan, "Startup Cost: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Startup Cost: ");
+ 		*startup_cost = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for startup cost%c", *endp);
+ 	}
+ 
+ 	/* extract total cost from remote plan */
+ 	p = strstr(plan, "Total Cost: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Total Cost: ");
+ 		*total_cost = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for total cost");
+ 	}
+ 
+ 	/* extract # of rows from remote plan */
+ 	p = strstr(plan, "Plan Rows: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Plan Rows: ");
+ 		baserel->rows = strtod(p, &endp);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for plan rows");
+ 	}
+ 
+ 	/* extract average width from remote plan */
+ 	p = strstr(plan, "Plan Width: ");
+ 	if (p != NULL)
+ 	{
+ 		p += strlen("Plan Width: ");
+ 		baserel->width = strtol(p, &endp, 10);
+ 		if (*endp != '\n' && *endp != '\0')
+ 			elog(ERROR, "invalid plan format for plan width");
+ 	}
+ 
+ 	/* TODO Selectivity of quals pushed down should be considered. */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Mark that this scan has opened a cursor. */
+ 		festate->cursor_opened = true;
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(MessageContext);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...fb49ffb .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...965193b .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,184 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp
+ ) SERVER loopback2;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101;
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index adf09ca..65c7e81 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 7a698e5..2dd41f0 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 124,129 ****
--- 124,130 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...22f795e .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,252 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   The <application>pgsql_fdw</application> can be installed on only
+   <productname>PostgreSQL</productname> 9.1 or later, but it can also access
+   data stored in <productname>PostgreSQL</productname> 9.0.
+   <productname>PostgreSQL</productname>8.4 or older are not available as remote
+   server because <application>pgsql_fdw</application> uses YAML format of
+   <command>EXPLAIN</command> output.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until locla role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> executes <command>BEGIN</command>
+    command when a new connection has established.  This means that all remote
+    queries for a foreign server are executed in a transaction.  Since the
+    default transaction isolation level is <literal>READ COMMITTED</literal>,
+    multiple foreign scans in a local query might produce inconsistent results.
+ 
+    To avoid this inconsistency, you can use <literal>SERIALIZABLE</literal>
+    level for remote transaction with setting
+    <literal>default_transaction_isolation</literal> for the user used for
+    <application>pgsql_fdw</application> connection on remote side.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding some basic costs:  connection costs, remote query costs and
+    data transfer costs.
+    To get remote query costs <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+ 
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                           QUERY PLAN
+ -----------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8769.00 rows=1 width=4)
+    Remote SQL: SELECT aid, NULL, NULL, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
+ (2 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 75923a6..0aae9d2 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 8a1c82e..a56366f 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 626,631 ****
--- 626,632 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 1cf3b3c..4a7ffa6 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 26,32 ****
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 26,32 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 345,398 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 345,373 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..d809cac 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 235,238 ****
--- 235,392 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum, const char *optname);
+ </programlisting>
+ 
+      This function returns a copied string (created in current memory context)
+      of the value of a FDW option with given name which is set on a object with
+      given oid and attribute number.  This function ignores catalogs if invalid
+      identifir is given for it.
+ 
+      <itemizedlist>
+       <listitem>
+        <para>
+         If attnum is <literal>InvalidAttrNumber</literal> or relid is
+         <literal>Invalidoid</literal>, <structname>pg_attribute</structname> is
+         ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If relid is <literal>InvalidOid</literal>,
+         <structname>pg_foreign_table</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If both serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_server</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If all of fdwid, serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_data_wrapper</structname> is ignored.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+ 
+     <para>
+      If the option with given name is set in multiple object level, the one in
+      the finest-grained object is used; e.g. priority is given to user mappings 
+      over than foreign servers.
+      This function would be useful when you know which option is needed but you
+      don't know where it is set.  If you already know the source object, it
+      would be more efficient to use object retrieval functions.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index a7d30a1..b984a5e 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
*************** GetForeignTable(Oid relid)
*** 248,253 ****
--- 248,378 ----
  
  
  /*
+  * If an option entry which matches the given name was found in the given
+  * list, returns a copy of arg string, otherwise returns NULL.
+  */
+ static char *
+ get_options_value(List *options, const char *optname)
+ {
+ 	ListCell   *lc;
+ 
+ 	/* Find target option from the list. */
+ 	foreach (lc, options)
+ 	{
+ 		DefElem	   *def = lfirst(lc);
+ 
+ 		if (strcmp(def->defname, optname) == 0)
+ 			return pstrdup(strVal(def->arg));
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ /*
+  * Returns a copy of the value of specified option with searching the option
+  * from appropriate catalog.  If an option was stored in multiple object
+  * levels, one in the finest-grained object level is used; lookup order is:
+  *   1) pg_attribute (only when both attnum and relid are valid)
+  *   2) pg_foreign_table (only when relid is valid)
+  *   3) pg_user_mapping (only when serverid or relid is valid)
+  *   4) pg_foreign_server (only when serverid or relid is valid)
+  *   5) pg_foreign_data_wrapper (only when fdwid or serverid or relid is valid)
+  * This priority rule would be useful in most cases using FDW options.
+  *
+  * If attnum was InvalidAttrNumber, we don't retrieve FDW optiosn from
+  * pg_attribute.attfdwoptions.
+  */
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum,
+ 				  const char *optname)
+ {
+ 	ForeignTable   *table = NULL;
+ 	UserMapping	   *user = NULL;
+ 	ForeignServer  *server = NULL;
+ 	ForeignDataWrapper  *wrapper = NULL;
+ 	char		   *value;
+ 
+ 	/* Do we need to search pg_attribute? */
+ 	if (attnum != InvalidAttrNumber && relid != InvalidOid)
+ 	{
+ 		value = get_options_value(GetForeignColumnOptions(relid, attnum),
+ 								  optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_table? */
+ 	if (relid != InvalidOid)
+ 	{
+ 		table = GetForeignTable(relid);
+ 		value = get_options_value(table->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		serverid = table->serverid;
+ 	}
+ 
+ 	/* Do we need to search pg_user_mapping and pg_foreign_server? */
+ 	if (serverid != InvalidOid)
+ 	{
+ 		user = GetUserMapping(GetOuterUserId(), serverid);
+ 		value = get_options_value(user->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		server = GetForeignServer(serverid);
+ 		value = get_options_value(server->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		fdwid = server->fdwid;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_data_wrapper? */
+ 	if (fdwid != InvalidOid)
+ 	{
+ 		wrapper = GetForeignDataWrapper(fdwid);
+ 		value = get_options_value(wrapper->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ 
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
+ 
+ /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
   * to get its FdwRoutine struct.
   */
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 2c436ae..6498162 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,83 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern char *GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid,
+ 							AttrNumber attnum, const char *optname);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/Makefile b/contrib/Makefile
index 0c238aa..e09e61e 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...b497dab .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,508 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 	PGconn		   *conn = NULL;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/* Is there any cached and valid connection with such key? */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (found)
+ 	{
+ 		if (entry->conn != NULL)
+ 		{
+ 			entry->refs++;
+ 			elog(DEBUG1,
+ 				 "reuse connection %u/%u (%d)",
+ 				 entry->serverid,
+ 				 entry->userid,
+ 				 entry->refs);
+ 			return entry->conn;
+ 		}
+ 
+ 		/*
+ 		 * Connection cache entry was found but connection in it is invalid.
+ 		 * We reuse entry to store newly established connection later.
+ 		 */
+ 	}
+ 	else
+ 	{
+ 		/*
+ 		 * Use ResourceOwner to clean the connection up on error including
+ 		 * user interrupt.
+ 		 */
+ 		elog(DEBUG1,
+ 			 "create entry for %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * Here we have to establish new connection.
+ 	 * Use PG_TRY block to ensure closing connection on error.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		/* Connect to the foreign PostgreSQL server */
+ 		conn = connect_pg_server(server, user);
+ 
+ 		/*
+ 		 * Initialize the cache entry to keep new connection.
+ 		 * Note: key items of entry has been initialized in
+ 		 * hash_search(HASH_ENTER).
+ 		 */
+ 		entry->refs = 1;
+ 		entry->conn = conn;
+ 		elog(DEBUG1,
+ 			 "connected to %u/%u (%d)",
+ 			 entry->serverid,
+ 			 entry->userid,
+ 			 entry->refs);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQfinish(conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	/*
+ 	 * Start transaction to use cursor to retrieve data separately.
+ 	 */
+ 	res = PQexec(conn, "BEGIN");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction");
+ 	}
+ 	PQclear(res);
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If the caller was the last referrer, unregister it from cache.
+ 	 * TODO: Note that sharing connections requires a mechanism to detect
+ 	 * change of FDW object to invalidate lasting connections.
+ 	 */
+ 	entry->refs--;
+ 	elog(DEBUG1,
+ 		 "connection %u/%u released (%d)",
+ 		 entry->serverid,
+ 		 entry->userid,
+ 		 entry->refs);
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		elog(DEBUG1,
+ 			 "closing connection %u/%u",
+ 			 entry->serverid,
+ 			 entry->userid);
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ 	else
+ 		elog(DEBUG1,
+ 			 "connection %u/%u already closed",
+ 			 entry->serverid,
+ 			 entry->userid);
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			elog(DEBUG1, "found: %u/%u", entry->serverid, entry->userid);
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 	elog(DEBUG1, "closed connection %u/%u", serverid, userid);
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...694534f .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...def5cb3 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,199 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname;
+ 
+ 				/* Ignore dropped attributes. */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					continue;
+ 
+ 				colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 											attr, "colname");
+ 				if (colname == NULL)
+ 					colname = strVal(list_nth(rte->eref->colnames, attr - 1));
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...dfac57a .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,526 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                  QUERY PLAN                                                                  
+ ---------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Nested Loop
+          Join Filter: (t1.c3 = t2.c3)
+          ->  HashAggregate
+                ->  Foreign Scan on ft2 t2
+                      Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                      Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (11 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                  QUERY PLAN                                                                  
+ ---------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Nested Loop
+          Join Filter: (t1.c3 = t2.c3)
+          ->  HashAggregate
+                ->  Foreign Scan on ft2 t2
+                      Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                      Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (11 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...e123cba .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...54ffae9 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,850 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ 	bool		cursor_opened;	/* true if cursor has been opened */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	FdwRoutine *fdwroutine = makeNode(FdwRoutine);
+ 
+ 	fdwroutine->PlanForeignScan = pgsqlPlanForeignScan;
+ 	fdwroutine->ExplainForeignScan = pgsqlExplainForeignScan;
+ 	fdwroutine->BeginForeignScan = pgsqlBeginForeignScan;
+ 	fdwroutine->IterateForeignScan = pgsqlIterateForeignScan;
+ 	fdwroutine->ReScanForeignScan = pgsqlReScanForeignScan;
+ 	fdwroutine->EndForeignScan = pgsqlEndForeignScan;
+ 
+ 	PG_RETURN_POINTER(fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 	festate->cursor_opened = false;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL && !festate->cursor_opened)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (!festate->cursor_opened)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	if (festate->tuples != NULL)
+ 		tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (!festate->cursor_opened)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	if (festate->tuples != NULL)
+ 	{
+ 		tuplestore_end(festate->tuples);
+ 		festate->tuples = NULL;
+ 	}
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* goundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 		plan = pstrdup(PQgetvalue(res, 0, 0));
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * Find estimation portion from top plan node. Here we search open
+ 	 * parentheses from end of line to avoid finding unexpected parentheses.
+ 	 */
+ 	p = strrchr(plan, '(');
+ 	if (p == NULL)
+ 		elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 	n = sscanf(p,
+ 			   "(cost=%lf..%lf rows=%lf width=%d)",
+ 			   startup_cost,
+ 			   total_cost,
+ 			   &baserel->rows,
+ 			   &baserel->width);
+ 	if (n != 4)
+ 		elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Mark that this scan has opened a cursor. */
+ 		festate->cursor_opened = true;
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(MessageContext);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...fb49ffb .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2011, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...7f9f9cc .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,212 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index adf09ca..65c7e81 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 7a698e5..2dd41f0 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 124,129 ****
--- 124,130 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...299f4b6 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,244 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until locla role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> executes <command>BEGIN</command>
+    command when a new connection has established.  This means that all remote
+    queries for a foreign server are executed in a transaction.  Since the
+    default transaction isolation level is <literal>READ COMMITTED</literal>,
+    multiple foreign scans in a local query might produce inconsistent results.
+ 
+    To avoid this inconsistency, you can use <literal>SERIALIZABLE</literal>
+    level for remote transaction with setting
+    <literal>default_transaction_isolation</literal> for the user used for
+    <application>pgsql_fdw</application> connection on remote side.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding some basic costs:  connection costs, remote query costs and
+    data transfer costs.
+    To get remote query costs <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+ 
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8046.37 rows=301037 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 29df748..a1de09d 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 994dc53..ccb186b 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 642,647 ****
--- 642,648 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index def5cb3..26b410d 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 35,43 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
  deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
--- 35,48 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
  deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 51,56 ****
--- 56,62 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 59,65 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
--- 65,79 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 75,80 ****
--- 89,98 ----
  			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
  			List		   *attrs;
  
+ 			/* Determine whether the qual can be pushed down or not. */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 
  			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 193,199 ****
--- 211,408 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	Oid		func;
+ 
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down bacause
+ 	 * it might has uncompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down bacause it might has uncompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	/*
+ 	 * If function used by the expression is not built-in, it can't be pushed
+ 	 * down bacause it might has uncompatible semantics on remote side.
+ 	 */
+ 	func = exprFunction(node);
+ 	if (func != InvalidOid && !is_builtin(func))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 		case T_FuncExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index dfac57a..2166fb4 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 218,229 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
     Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 218,229 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
     Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 331,349 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
--- 331,349 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
  (3 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
*************** DROP FUNCTION pgsql_fdw_abs(int);
*** 354,370 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
           Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 354,369 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
           Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Filter: (c1 = 2)
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (7 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 381,388 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                  QUERY PLAN                                                                  
! ---------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Nested Loop
--- 380,387 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                            QUERY PLAN                                                                            
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Nested Loop
*************** EXPLAIN (COSTS false) EXECUTE st2(10, 20
*** 390,399 ****
           ->  HashAggregate
                 ->  Foreign Scan on ft2 t2
                       Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                      Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (11 rows)
  
  EXECUTE st2(10, 20);
--- 389,398 ----
           ->  HashAggregate
                 ->  Foreign Scan on ft2 t2
                       Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                      Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
  (11 rows)
  
  EXECUTE st2(10, 20);
*************** EXECUTE st1(101, 101);
*** 411,418 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                  QUERY PLAN                                                                  
! ---------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Nested Loop
--- 410,417 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                            QUERY PLAN                                                                            
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Nested Loop
*************** EXPLAIN (COSTS false) EXECUTE st3(10, 20
*** 420,429 ****
           ->  HashAggregate
                 ->  Foreign Scan on ft2 t2
                       Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                      Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (11 rows)
  
  EXECUTE st3(10, 20);
--- 419,428 ----
           ->  HashAggregate
                 ->  Foreign Scan on ft2 t2
                       Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                      Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
  (11 rows)
  
  EXECUTE st3(10, 20);
*************** EXECUTE st3(20, 30);
*** 441,491 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  -- cleanup
--- 440,490 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  -- cleanup
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index 299f4b6..1715257 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 225,235 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8046.37 rows=301037 width=8)
     Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
  (3 rows)
  </synopsis>
   </sect2>
--- 225,235 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! -------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8798.96 rows=1 width=97)
     Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT aid, bid, abalance, filler FROM public.pgbench_accounts WHERE (abalance < 0)
  (3 rows)
  </synopsis>
   </sect2>
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 48b0590..f2acd46 100644
*** a/src/backend/nodes/nodeFuncs.c
--- b/src/backend/nodes/nodeFuncs.c
*************** leftmostLoc(int loc1, int loc2)
*** 1405,1410 ****
--- 1405,1447 ----
  		return Min(loc1, loc2);
  }
  
+ /*
+  *	exprFunction -
+  *	  returns the Oid of the function used by the expression's.
+  */
+ Oid
+ exprFunction(const Node *expr)
+ {
+ 	Oid			func;
+ 
+ 	if (!expr)
+ 		return InvalidOid;
+ 
+ 	switch (nodeTag(expr))
+ 	{
+ 		case T_Aggref:
+ 			func = ((const Aggref *) expr)->aggfnoid;
+ 			break;
+ 		case T_WindowFunc:
+ 			func = ((const WindowFunc *) expr)->winfnoid;
+ 			break;
+ 		case T_FuncExpr:
+ 			func = ((const FuncExpr *) expr)->funcid;
+ 			break;
+ 		case T_OpExpr:
+ 			func = ((const OpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			func = ((const ScalarArrayOpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ArrayCoerceExpr:
+ 			func = ((const ArrayCoerceExpr *) expr)->elemfuncid;
+ 			break;
+ 		default:
+ 			func = InvalidOid;
+ 	}
+ 	return func;
+ }
  
  /*
   * Standard expression-tree walking support
diff --git a/src/include/nodes/nodeFuncs.h b/src/include/nodes/nodeFuncs.h
index 4980dd8..09d877f 100644
*** a/src/include/nodes/nodeFuncs.h
--- b/src/include/nodes/nodeFuncs.h
*************** extern void exprSetInputCollation(Node *
*** 38,43 ****
--- 38,45 ----
  
  extern int	exprLocation(const Node *expr);
  
+ extern Oid	exprFunction(const Node *expr);
+ 
  extern bool expression_tree_walker(Node *node, bool (*walker) (),
  											   void *context);
  extern Node *expression_tree_mutator(Node *node, Node *(*mutator) (),

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index cf9e775..3645189 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 35,43 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
  deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
--- 35,48 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
  deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 51,56 ****
--- 56,62 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 59,65 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
--- 65,79 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 75,80 ****
--- 89,98 ----
  			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
  			List		   *attrs;
  
+ 			/* Determine whether the qual can be pushed down or not. */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 
  			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 193,199 ****
--- 211,408 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	Oid		func;
+ 
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down bacause
+ 	 * it might has uncompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down bacause it might has uncompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	/*
+ 	 * If function used by the expression is not built-in, it can't be pushed
+ 	 * down bacause it might has uncompatible semantics on remote side.
+ 	 */
+ 	func = exprFunction(node);
+ 	if (func != InvalidOid && !is_builtin(func))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 		case T_FuncExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index 7aab32c..7a1e9e3 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 218,229 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
     Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 218,229 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
     Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 331,349 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
--- 331,349 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
  (3 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
*************** DROP FUNCTION pgsql_fdw_abs(int);
*** 354,370 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
           Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 354,369 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
           Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Filter: (c1 = 2)
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (7 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 381,400 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
  (12 rows)
  
  EXECUTE st2(10, 20);
--- 380,399 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
  (12 rows)
  
  EXECUTE st2(10, 20);
*************** EXECUTE st1(101, 101);
*** 412,431 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
  (12 rows)
  
  EXECUTE st3(10, 20);
--- 411,430 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
  (12 rows)
  
  EXECUTE st3(10, 20);
*************** EXECUTE st3(20, 30);
*** 443,493 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  -- cleanup
--- 442,492 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
  (3 rows)
  
  -- cleanup
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index 299f4b6..1715257 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 225,235 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8046.37 rows=301037 width=8)
     Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
  (3 rows)
  </synopsis>
   </sect2>
--- 225,235 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! -------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8798.96 rows=1 width=97)
     Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT aid, bid, abalance, filler FROM public.pgbench_accounts WHERE (abalance < 0)
  (3 rows)
  </synopsis>
   </sect2>
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 51459c4..c017d6b 100644
*** a/src/backend/nodes/nodeFuncs.c
--- b/src/backend/nodes/nodeFuncs.c
*************** leftmostLoc(int loc1, int loc2)
*** 1405,1410 ****
--- 1405,1449 ----
  		return Min(loc1, loc2);
  }
  
+ /*
+  *	exprFunction -
+  *	  returns the Oid of the function used by the expression.
+  *
+  * Result is InvalidOid if the node type doesn't store this information.
+  */
+ Oid
+ exprFunction(const Node *expr)
+ {
+ 	Oid			func;
+ 
+ 	if (!expr)
+ 		return InvalidOid;
+ 
+ 	switch (nodeTag(expr))
+ 	{
+ 		case T_Aggref:
+ 			func = ((const Aggref *) expr)->aggfnoid;
+ 			break;
+ 		case T_WindowFunc:
+ 			func = ((const WindowFunc *) expr)->winfnoid;
+ 			break;
+ 		case T_FuncExpr:
+ 			func = ((const FuncExpr *) expr)->funcid;
+ 			break;
+ 		case T_OpExpr:
+ 			func = ((const OpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			func = ((const ScalarArrayOpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ArrayCoerceExpr:
+ 			func = ((const ArrayCoerceExpr *) expr)->elemfuncid;
+ 			break;
+ 		default:
+ 			func = InvalidOid;
+ 	}
+ 	return func;
+ }
  
  /*
   * Standard expression-tree walking support
diff --git a/src/include/nodes/nodeFuncs.h b/src/include/nodes/nodeFuncs.h
index def4f31..a3ebe5c 100644
*** a/src/include/nodes/nodeFuncs.h
--- b/src/include/nodes/nodeFuncs.h
*************** extern void exprSetInputCollation(Node *
*** 38,43 ****
--- 38,45 ----
  
  extern int	exprLocation(const Node *expr);
  
+ extern Oid	exprFunction(const Node *expr);
+ 
  extern bool expression_tree_walker(Node *node, bool (*walker) (),
  											   void *context);
  extern Node *expression_tree_mutator(Node *node, Node *(*mutator) (),

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...99d8fad .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,558 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increment connection reference counter. */
+ 	entry->refs++;
+ 
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * Before starting transaction, we abort old transaction just in case.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(entry->conn);
+ 		begin_remote_tx(entry->conn);
+ 	}
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql;
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+ 			break;
+ 		case XACT_READ_COMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+ 			break;
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrement reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...cf9e775 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,199 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname;
+ 
+ 				/* Ignore dropped attributes. */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					continue;
+ 
+ 				colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 											attr, "colname");
+ 				if (colname == NULL)
+ 					colname = strVal(list_nth(rte->eref->colnames, attr - 1));
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...7aab32c .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,528 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...65e3c54 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...9ded3e1 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,859 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 	T_FdwRoutine,
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(MessageContext,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...7f9f9cc .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,212 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...299f4b6 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,244 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until locla role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> executes <command>BEGIN</command>
+    command when a new connection has established.  This means that all remote
+    queries for a foreign server are executed in a transaction.  Since the
+    default transaction isolation level is <literal>READ COMMITTED</literal>,
+    multiple foreign scans in a local query might produce inconsistent results.
+ 
+    To avoid this inconsistency, you can use <literal>SERIALIZABLE</literal>
+    level for remote transaction with setting
+    <literal>default_transaction_isolation</literal> for the user used for
+    <application>pgsql_fdw</application> connection on remote side.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding some basic costs:  connection costs, remote query costs and
+    data transfer costs.
+    To get remote query costs <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+ 
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8046.37 rows=301037 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9ad54c5..c2a5a7b 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 68179d5..e4bd8eb 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 648,653 ****
--- 648,654 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 46394a8..a522e36 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 26,32 ****
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 26,32 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 345,398 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 345,373 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..d809cac 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 235,238 ****
--- 235,392 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum, const char *optname);
+ </programlisting>
+ 
+      This function returns a copied string (created in current memory context)
+      of the value of a FDW option with given name which is set on a object with
+      given oid and attribute number.  This function ignores catalogs if invalid
+      identifir is given for it.
+ 
+      <itemizedlist>
+       <listitem>
+        <para>
+         If attnum is <literal>InvalidAttrNumber</literal> or relid is
+         <literal>Invalidoid</literal>, <structname>pg_attribute</structname> is
+         ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If relid is <literal>InvalidOid</literal>,
+         <structname>pg_foreign_table</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If both serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_server</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If all of fdwid, serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_data_wrapper</structname> is ignored.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+ 
+     <para>
+      If the option with given name is set in multiple object level, the one in
+      the finest-grained object is used; e.g. priority is given to user mappings 
+      over than foreign servers.
+      This function would be useful when you know which option is needed but you
+      don't know where it is set.  If you already know the source object, it
+      would be more efficient to use object retrieval functions.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index c4c2a61..8e98f0f 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
*************** GetForeignTable(Oid relid)
*** 248,253 ****
--- 248,378 ----
  
  
  /*
+  * If an option entry which matches the given name was found in the given
+  * list, returns a copy of arg string, otherwise returns NULL.
+  */
+ static char *
+ get_options_value(List *options, const char *optname)
+ {
+ 	ListCell   *lc;
+ 
+ 	/* Find target option from the list. */
+ 	foreach (lc, options)
+ 	{
+ 		DefElem	   *def = lfirst(lc);
+ 
+ 		if (strcmp(def->defname, optname) == 0)
+ 			return pstrdup(strVal(def->arg));
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ /*
+  * Returns a copy of the value of specified option with searching the option
+  * from appropriate catalog.  If an option was stored in multiple object
+  * levels, one in the finest-grained object level is used; lookup order is:
+  *   1) pg_attribute (only when both attnum and relid are valid)
+  *   2) pg_foreign_table (only when relid is valid)
+  *   3) pg_user_mapping (only when serverid or relid is valid)
+  *   4) pg_foreign_server (only when serverid or relid is valid)
+  *   5) pg_foreign_data_wrapper (only when fdwid or serverid or relid is valid)
+  * This priority rule would be useful in most cases using FDW options.
+  *
+  * If attnum was InvalidAttrNumber, we don't retrieve FDW optiosn from
+  * pg_attribute.attfdwoptions.
+  */
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum,
+ 				  const char *optname)
+ {
+ 	ForeignTable   *table = NULL;
+ 	UserMapping	   *user = NULL;
+ 	ForeignServer  *server = NULL;
+ 	ForeignDataWrapper  *wrapper = NULL;
+ 	char		   *value;
+ 
+ 	/* Do we need to search pg_attribute? */
+ 	if (attnum != InvalidAttrNumber && relid != InvalidOid)
+ 	{
+ 		value = get_options_value(GetForeignColumnOptions(relid, attnum),
+ 								  optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_table? */
+ 	if (relid != InvalidOid)
+ 	{
+ 		table = GetForeignTable(relid);
+ 		value = get_options_value(table->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		serverid = table->serverid;
+ 	}
+ 
+ 	/* Do we need to search pg_user_mapping and pg_foreign_server? */
+ 	if (serverid != InvalidOid)
+ 	{
+ 		user = GetUserMapping(GetOuterUserId(), serverid);
+ 		value = get_options_value(user->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		server = GetForeignServer(serverid);
+ 		value = get_options_value(server->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		fdwid = server->fdwid;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_data_wrapper? */
+ 	if (fdwid != InvalidOid)
+ 	{
+ 		wrapper = GetForeignDataWrapper(fdwid);
+ 		value = get_options_value(wrapper->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ 
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
+ 
+ /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
   * to get its FdwRoutine struct.
   */
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 191122d..e25b871 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,83 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern char *GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid,
+ 							AttrNumber attnum, const char *optname);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 46394a8..a522e36 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 26,32 ****
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 26,32 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 345,398 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 345,373 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..d809cac 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 235,238 ****
--- 235,392 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum, const char *optname);
+ </programlisting>
+ 
+      This function returns a copied string (created in current memory context)
+      of the value of a FDW option with given name which is set on a object with
+      given oid and attribute number.  This function ignores catalogs if invalid
+      identifir is given for it.
+ 
+      <itemizedlist>
+       <listitem>
+        <para>
+         If attnum is <literal>InvalidAttrNumber</literal> or relid is
+         <literal>Invalidoid</literal>, <structname>pg_attribute</structname> is
+         ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If relid is <literal>InvalidOid</literal>,
+         <structname>pg_foreign_table</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If both serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_server</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If all of fdwid, serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_data_wrapper</structname> is ignored.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+ 
+     <para>
+      If the option with given name is set in multiple object level, the one in
+      the finest-grained object is used; e.g. priority is given to user mappings 
+      over than foreign servers.
+      This function would be useful when you know which option is needed but you
+      don't know where it is set.  If you already know the source object, it
+      would be more efficient to use object retrieval functions.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index c4c2a61..8e98f0f 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
*************** GetForeignTable(Oid relid)
*** 248,253 ****
--- 248,378 ----
  
  
  /*
+  * If an option entry which matches the given name was found in the given
+  * list, returns a copy of arg string, otherwise returns NULL.
+  */
+ static char *
+ get_options_value(List *options, const char *optname)
+ {
+ 	ListCell   *lc;
+ 
+ 	/* Find target option from the list. */
+ 	foreach (lc, options)
+ 	{
+ 		DefElem	   *def = lfirst(lc);
+ 
+ 		if (strcmp(def->defname, optname) == 0)
+ 			return pstrdup(strVal(def->arg));
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ /*
+  * Returns a copy of the value of specified option with searching the option
+  * from appropriate catalog.  If an option was stored in multiple object
+  * levels, one in the finest-grained object level is used; lookup order is:
+  *   1) pg_attribute (only when both attnum and relid are valid)
+  *   2) pg_foreign_table (only when relid is valid)
+  *   3) pg_user_mapping (only when serverid or relid is valid)
+  *   4) pg_foreign_server (only when serverid or relid is valid)
+  *   5) pg_foreign_data_wrapper (only when fdwid or serverid or relid is valid)
+  * This priority rule would be useful in most cases using FDW options.
+  *
+  * If attnum was InvalidAttrNumber, we don't retrieve FDW optiosn from
+  * pg_attribute.attfdwoptions.
+  */
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum,
+ 				  const char *optname)
+ {
+ 	ForeignTable   *table = NULL;
+ 	UserMapping	   *user = NULL;
+ 	ForeignServer  *server = NULL;
+ 	ForeignDataWrapper  *wrapper = NULL;
+ 	char		   *value;
+ 
+ 	/* Do we need to search pg_attribute? */
+ 	if (attnum != InvalidAttrNumber && relid != InvalidOid)
+ 	{
+ 		value = get_options_value(GetForeignColumnOptions(relid, attnum),
+ 								  optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_table? */
+ 	if (relid != InvalidOid)
+ 	{
+ 		table = GetForeignTable(relid);
+ 		value = get_options_value(table->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		serverid = table->serverid;
+ 	}
+ 
+ 	/* Do we need to search pg_user_mapping and pg_foreign_server? */
+ 	if (serverid != InvalidOid)
+ 	{
+ 		user = GetUserMapping(GetOuterUserId(), serverid);
+ 		value = get_options_value(user->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		server = GetForeignServer(serverid);
+ 		value = get_options_value(server->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		fdwid = server->fdwid;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_data_wrapper? */
+ 	if (fdwid != InvalidOid)
+ 	{
+ 		wrapper = GetForeignDataWrapper(fdwid);
+ 		value = get_options_value(wrapper->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ 
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
+ 
+ /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
   * to get its FdwRoutine struct.
   */
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 191122d..e25b871 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,83 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern char *GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid,
+ 							AttrNumber attnum, const char *optname);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...6ede259 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,553 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql;
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+ 			break;
+ 		case XACT_READ_COMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+ 			break;
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...cf9e775 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,199 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname;
+ 
+ 				/* Ignore dropped attributes. */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					continue;
+ 
+ 				colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 											attr, "colname");
+ 				if (colname == NULL)
+ 					colname = strVal(list_nth(rte->eref->colnames, attr - 1));
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...7aab32c .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,528 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...65e3c54 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...a649669 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,879 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 	T_FdwRoutine,
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(MessageContext,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...7f9f9cc .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,212 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...c9d5d8f .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,253 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    The transaction isolation level used for remote transaction is same as
+    local transaction.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9ad54c5..c2a5a7b 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 2c331ce..dc6932a 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 648,653 ****
--- 648,654 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index cf9e775..594743f 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 35,46 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
--- 35,53 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel, bool *has_param)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 51,56 ****
--- 58,64 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 59,73 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
  	if (baserel->baserestrictinfo != NIL)
  	{
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
--- 67,91 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
+ 	*has_param = false;
  	if (baserel->baserestrictinfo != NIL)
  	{
+ 		List	   *local_qual = NIL;
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 76,81 ****
--- 94,113 ----
  			List		   *attrs;
  
  			/*
+ 			 * Determine whether the qual can be pushed down or not.  If a qual
+ 			 * can be pushed down and it contains external param, tell that to
+ 			 * caller in order to fall back to fixed costs.
+ 			 */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 			{
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 				if (contain_ext_param((Node*) ri->clause))
+ 					*has_param = true;
+ 			}
+ 			else
+ 				local_qual = lappend(local_qual, ri);
+ 
+ 			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
  			 * SELECT clause of remote query.  We can ignore attributes
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 87,92 ****
--- 119,130 ----
  									PVC_RECURSE_PLACEHOLDERS);
  			attr_used = list_union(attr_used, attrs);
  		}
+ 
+ 		/*
+ 		 * Remove pushed down qualifiers from baserestrictinfo to avoid
+ 		 * redundant evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
  	}
  
  	/*
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 193,199 ****
--- 231,461 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	Oid		func;
+ 
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	/*
+ 	 * If function used by the expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	func = exprFunction(node);
+ 	if (func != InvalidOid && !is_builtin(func))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 		case T_FuncExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index 7aab32c..afd9e19 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 218,229 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 218,229 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: (((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 331,350 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
  DROP FUNCTION pgsql_fdw_abs(int);
--- 331,348 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
! (2 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
! (2 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
  DROP FUNCTION pgsql_fdw_abs(int);
*************** DROP FUNCTION pgsql_fdw_abs(int);
*** 354,370 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 352,365 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (5 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 381,401 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 376,395 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c4) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st1(101, 101);
*** 412,432 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 406,425 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c5) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st3(20, 30);
*** 443,494 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- cleanup
  DEALLOCATE st1;
--- 436,481 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  -- cleanup
  DEALLOCATE st1;
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index a649669..86abd0a 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
*************** static void estimate_costs(PlannerInfo *
*** 123,130 ****
  static void execute_query(ForeignScanState *node);
  static PGresult *fetch_result(ForeignScanState *node);
  static void store_result(ForeignScanState *node, PGresult *res);
- static bool contain_ext_param(Node *clause);
- static bool contain_ext_param_walker(Node *node, void *context);
  
  /* Exported functions, but not written in pgsql_fdw.h. */
  void _PG_init(void);
--- 123,128 ----
*************** pgsqlPlanForeignScan(Oid foreigntableid,
*** 188,201 ****
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
! 	sql = deparseSql(foreigntableid, root, baserel);
  	table = GetForeignTable(foreigntableid);
  	server = GetForeignServer(table->serverid);
! 	estimate_costs(root, baserel, sql, server->serverid,
! 				   &fdwplan->startup_cost, &fdwplan->total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
--- 186,216 ----
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
+ 	bool			has_param;
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
! 	sql = deparseSql(foreigntableid, root, baserel, &has_param);
  	table = GetForeignTable(foreigntableid);
  	server = GetForeignServer(table->serverid);
! 
! 	/*
! 	 * If the baserestrictinfo contains any Param node with paramkind
! 	 * PARAM_EXTERNAL as part of push-down-able condition, we need to
! 	 * groundless fixed costs because we can't get actual parameter values
! 	 * here, so we use fixed and large costs as second best so that planner
! 	 * tend to choose custom plan.
! 	 *
! 	 * See comments in plancache.c for details of custom plan.
! 	 */
! 	if (has_param)
! 	{
! 		fdwplan->startup_cost = CONNECTION_COSTS;
! 		fdwplan->total_cost = 10000;	/* groundless large costs */
! 	}
! 	else
! 		estimate_costs(root, baserel, sql, server->serverid,
! 					   &fdwplan->startup_cost, &fdwplan->total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
*************** estimate_costs(PlannerInfo *root, RelOpt
*** 541,547 ****
  			   const char *sql, Oid serverid,
  			   Cost *startup_cost, Cost *total_cost)
  {
- 	ListCell	   *lc;
  	ForeignServer  *server;
  	UserMapping	   *user;
  	PGconn		   *conn = NULL;
--- 556,561 ----
*************** estimate_costs(PlannerInfo *root, RelOpt
*** 552,578 ****
  	int				n;
  
  	/*
- 	 * If the baserestrictinfo contains any Param node with paramkind
- 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
- 	 * simple SELECT statement.  However, we can't get actual parameter values
- 	 * here, so we use fixed and large costs as second best so that planner
- 	 * tend to choose custom plan.
- 	 *
- 	 * See comments in plancache.c for details of custom plan.
- 	 */
- 	foreach(lc, baserel->baserestrictinfo)
- 	{
- 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
- 		if (contain_ext_param((Node *) rs->clause))
- 		{
- 			*startup_cost = CONNECTION_COSTS;
- 			*total_cost = 10000;	/* groundless large costs */
- 
- 			return;
- 		}
- 	}
- 
- 	/*
  	 * Get connection to the foreign server.  Connection manager would
  	 * establish new connection if necessary.
  	 */
--- 566,571 ----
*************** store_result(ForeignScanState *node, PGr
*** 843,879 ****
  
  	tuplestore_donestoring(festate->tuples);
  }
- 
- /*
-  * contain_ext_param
-  *	  Recursively search for Param nodes within a clause.
-  *
-  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
-  *	  found.
-  *
-  * This does not descend into subqueries, and so should be used only after
-  * reduction of sublinks to subplans, or in contexts where it's known there
-  * are no subqueries.  There mustn't be outer-aggregate references either.
-  *
-  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
-  */
- static bool
- contain_ext_param(Node *clause)
- {
- 	return contain_ext_param_walker(clause, NULL);
- }
- 
- static bool
- contain_ext_param_walker(Node *node, void *context)
- {
- 	if (node == NULL)
- 		return false;
- 	if (IsA(node, Param))
- 	{
- 		Param	   *param = (Param *) node;
- 
- 		if (param->paramkind == PARAM_EXTERN)
- 			return true;		/* abort the tree traversal and return true */
- 	}
- 	return expression_tree_walker(node, contain_ext_param_walker, context);
- }
--- 836,838 ----
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index f6394ce..690d58b 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
*************** int ExtractConnectionOptions(List *defel
*** 23,28 ****
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
  
  #endif /* PGSQL_FDW_H */
--- 23,31 ----
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid,
! 				 PlannerInfo *root,
! 				 RelOptInfo *baserel,
! 				 bool *has_param);
  
  #endif /* PGSQL_FDW_H */
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index c9d5d8f..df2e7f6 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 234,245 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
!    Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
! (3 rows)
  </synopsis>
   </sect2>
  
--- 234,244 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! ------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8861.66 rows=518 width=8)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
! (2 rows)
  </synopsis>
   </sect2>
  
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 51459c4..c017d6b 100644
*** a/src/backend/nodes/nodeFuncs.c
--- b/src/backend/nodes/nodeFuncs.c
*************** leftmostLoc(int loc1, int loc2)
*** 1405,1410 ****
--- 1405,1449 ----
  		return Min(loc1, loc2);
  }
  
+ /*
+  *	exprFunction -
+  *	  returns the Oid of the function used by the expression.
+  *
+  * Result is InvalidOid if the node type doesn't store this information.
+  */
+ Oid
+ exprFunction(const Node *expr)
+ {
+ 	Oid			func;
+ 
+ 	if (!expr)
+ 		return InvalidOid;
+ 
+ 	switch (nodeTag(expr))
+ 	{
+ 		case T_Aggref:
+ 			func = ((const Aggref *) expr)->aggfnoid;
+ 			break;
+ 		case T_WindowFunc:
+ 			func = ((const WindowFunc *) expr)->winfnoid;
+ 			break;
+ 		case T_FuncExpr:
+ 			func = ((const FuncExpr *) expr)->funcid;
+ 			break;
+ 		case T_OpExpr:
+ 			func = ((const OpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			func = ((const ScalarArrayOpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ArrayCoerceExpr:
+ 			func = ((const ArrayCoerceExpr *) expr)->elemfuncid;
+ 			break;
+ 		default:
+ 			func = InvalidOid;
+ 	}
+ 	return func;
+ }
  
  /*
   * Standard expression-tree walking support
diff --git a/src/include/nodes/nodeFuncs.h b/src/include/nodes/nodeFuncs.h
index def4f31..a3ebe5c 100644
*** a/src/include/nodes/nodeFuncs.h
--- b/src/include/nodes/nodeFuncs.h
*************** extern void exprSetInputCollation(Node *
*** 38,43 ****
--- 38,45 ----
  
  extern int	exprLocation(const Node *expr);
  
+ extern Oid	exprFunction(const Node *expr);
+ 
  extern bool expression_tree_walker(Node *node, bool (*walker) (),
  											   void *context);
  extern Node *expression_tree_mutator(Node *node, Node *(*mutator) (),

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...6ede259 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,553 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql;
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+ 			break;
+ 		case XACT_READ_COMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+ 			break;
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...feea7b3 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,210 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 												attr, "colname");
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...9f2e282 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,532 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                          List of foreign-data wrappers
+    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                List of foreign servers
+    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+         List of user mappings
+   Server   | User name | FDW Options 
+ -----------+-----------+-------------
+  loopback1 | public    | 
+  loopback2 | public    | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  | usename  
+ -----------+----------
+  loopback2 | postgres
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for public
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...65e3c54 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...4e2ce84 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,885 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(MessageContext,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...f55bb14 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,216 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR public SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP EXTENSION pgsql_fdw CASCADE;
+ 
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...c9d5d8f .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,253 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    The transaction isolation level used for remote transaction is same as
+    local transaction.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9ad54c5..c2a5a7b 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 2c331ce..dc6932a 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 648,653 ****
--- 648,654 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

*** sql/pgsql_fdw.sql.orig	2012-02-13 19:52:08.000000000 +0900
--- sql/pgsql_fdw.sql	2012-02-13 19:44:17.000000000 +0900
***************
*** 2,7 ****
--- 2,19 ----
  -- create FDW objects
  -- ===================================================================
  
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
  CREATE EXTENSION pgsql_fdw;
  
  CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
***************
*** 168,173 ****
--- 180,186 ----
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
  DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
  DROP FUNCTION pgsql_fdw_abs(int);
  
  -- ===================================================================
***************
*** 212,216 ****
  -- ===================================================================
  -- cleanup
  -- ===================================================================
  DROP EXTENSION pgsql_fdw CASCADE;
! 
--- 225,231 ----
  -- ===================================================================
  -- cleanup
  -- ===================================================================
+ DROP SCHEMA "S 1" CASCADE;
  DROP EXTENSION pgsql_fdw CASCADE;
! \c
! DROP ROLE pgsql_fdw_user;

*** expected/pgsql_fdw.out.orig	2012-02-13 19:52:03.000000000 +0900
--- expected/pgsql_fdw.out	2012-02-13 19:51:49.000000000 +0900
***************
*** 1,6 ****
--- 1,13 ----
  -- ===================================================================
  -- create FDW objects
  -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
  CREATE EXTENSION pgsql_fdw;
  CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
  CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
***************
*** 130,147 ****
  ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
  ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
  \dew+
!                                          List of foreign-data wrappers
!    Name    |  Owner   |      Handler      |      Validator      | Access privileges | FDW Options | Description 
! -----------+----------+-------------------+---------------------+-------------------+-------------+-------------
!  pgsql_fdw | postgres | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
  (1 row)
  
  \des+
!                                                                                                                                                                                                                List of foreign servers
!    Name    |  Owner   | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
! -----------+----------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
!  loopback1 | postgres | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
!  loopback2 | postgres | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
  (2 rows)
  
  \deu+
--- 137,154 ----
  ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
  ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
  \dew+
!                                             List of foreign-data wrappers
!    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
! -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
!  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
  (1 row)
  
  \des+
!                                                                                                                                                                                                                   List of foreign servers
!    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
! -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
!  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
!  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
  (2 rows)
  
  \deu+
***************
*** 349,354 ****
--- 356,362 ----
  (2 rows)
  
  DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
  DROP FUNCTION pgsql_fdw_abs(int);
  -- ===================================================================
  -- parameterized queries
***************
*** 490,498 ****
  -- connection management
  -- ===================================================================
  SELECT srvname, usename FROM pgsql_fdw_connections;
!   srvname  | usename  
! -----------+----------
!  loopback2 | postgres
  (1 row)
  
  SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
--- 498,506 ----
  -- connection management
  -- ===================================================================
  SELECT srvname, usename FROM pgsql_fdw_connections;
!   srvname  |    usename     
! -----------+----------------
!  loopback2 | pgsql_fdw_user
  (1 row)
  
  SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
***************
*** 509,514 ****
--- 517,526 ----
  -- ===================================================================
  -- cleanup
  -- ===================================================================
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
  DROP EXTENSION pgsql_fdw CASCADE;
  NOTICE:  drop cascades to 6 other objects
  DETAIL:  drop cascades to server loopback1
***************
*** 517,519 ****
--- 529,533 ----
  drop cascades to user mapping for public
  drop cascades to foreign table ft1
  drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 46394a8..a522e36 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 26,32 ****
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 26,32 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 345,398 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 345,373 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..d809cac 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 235,238 ****
--- 235,392 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum, const char *optname);
+ </programlisting>
+ 
+      This function returns a copied string (created in current memory context)
+      of the value of a FDW option with given name which is set on a object with
+      given oid and attribute number.  This function ignores catalogs if invalid
+      identifir is given for it.
+ 
+      <itemizedlist>
+       <listitem>
+        <para>
+         If attnum is <literal>InvalidAttrNumber</literal> or relid is
+         <literal>Invalidoid</literal>, <structname>pg_attribute</structname> is
+         ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If relid is <literal>InvalidOid</literal>,
+         <structname>pg_foreign_table</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If both serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_server</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If all of fdwid, serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_data_wrapper</structname> is ignored.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+ 
+     <para>
+      If the option with given name is set in multiple object level, the one in
+      the finest-grained object is used; e.g. priority is given to user mappings 
+      over than foreign servers.
+      This function would be useful when you know which option is needed but you
+      don't know where it is set.  If you already know the source object, it
+      would be more efficient to use object retrieval functions.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index c4c2a61..8e98f0f 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
*************** GetForeignTable(Oid relid)
*** 248,253 ****
--- 248,378 ----
  
  
  /*
+  * If an option entry which matches the given name was found in the given
+  * list, returns a copy of arg string, otherwise returns NULL.
+  */
+ static char *
+ get_options_value(List *options, const char *optname)
+ {
+ 	ListCell   *lc;
+ 
+ 	/* Find target option from the list. */
+ 	foreach (lc, options)
+ 	{
+ 		DefElem	   *def = lfirst(lc);
+ 
+ 		if (strcmp(def->defname, optname) == 0)
+ 			return pstrdup(strVal(def->arg));
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ /*
+  * Returns a copy of the value of specified option with searching the option
+  * from appropriate catalog.  If an option was stored in multiple object
+  * levels, one in the finest-grained object level is used; lookup order is:
+  *   1) pg_attribute (only when both attnum and relid are valid)
+  *   2) pg_foreign_table (only when relid is valid)
+  *   3) pg_user_mapping (only when serverid or relid is valid)
+  *   4) pg_foreign_server (only when serverid or relid is valid)
+  *   5) pg_foreign_data_wrapper (only when fdwid or serverid or relid is valid)
+  * This priority rule would be useful in most cases using FDW options.
+  *
+  * If attnum was InvalidAttrNumber, we don't retrieve FDW optiosn from
+  * pg_attribute.attfdwoptions.
+  */
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum,
+ 				  const char *optname)
+ {
+ 	ForeignTable   *table = NULL;
+ 	UserMapping	   *user = NULL;
+ 	ForeignServer  *server = NULL;
+ 	ForeignDataWrapper  *wrapper = NULL;
+ 	char		   *value;
+ 
+ 	/* Do we need to search pg_attribute? */
+ 	if (attnum != InvalidAttrNumber && relid != InvalidOid)
+ 	{
+ 		value = get_options_value(GetForeignColumnOptions(relid, attnum),
+ 								  optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_table? */
+ 	if (relid != InvalidOid)
+ 	{
+ 		table = GetForeignTable(relid);
+ 		value = get_options_value(table->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		serverid = table->serverid;
+ 	}
+ 
+ 	/* Do we need to search pg_user_mapping and pg_foreign_server? */
+ 	if (serverid != InvalidOid)
+ 	{
+ 		user = GetUserMapping(GetOuterUserId(), serverid);
+ 		value = get_options_value(user->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		server = GetForeignServer(serverid);
+ 		value = get_options_value(server->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		fdwid = server->fdwid;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_data_wrapper? */
+ 	if (fdwid != InvalidOid)
+ 	{
+ 		wrapper = GetForeignDataWrapper(fdwid);
+ 		value = get_options_value(wrapper->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ 
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
+ 
+ /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
   * to get its FdwRoutine struct.
   */
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 191122d..e25b871 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,83 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern char *GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid,
+ 							AttrNumber attnum, const char *optname);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...6ede259 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,553 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql;
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+ 			break;
+ 		case XACT_READ_COMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+ 			break;
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */ 
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal. 
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */ 
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...feea7b3 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,210 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 * 
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 												attr, "colname");
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...7fe20e7 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,546 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                   List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...65e3c54 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time. 
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...4e2ce84 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,885 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw. 
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor 
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(MessageContext,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(node->ss.ps.state->es_query_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of CURSOR statement and fetch first bunch. */
+ 		PQclear(res);
+ 		res = fetch_result(node);
+ 
+ 		/*
+ 		 * Store the result of the query into tuplestore.
+ 		 * We must release PGresult here to avoid memory leak.
+ 		 */
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 	
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...42d26fd .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,231 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...c9d5d8f .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,253 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    The transaction isolation level used for remote transaction is same as
+    local transaction.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9ad54c5..c2a5a7b 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 2c331ce..dc6932a 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 648,653 ****
--- 648,654 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index feea7b3..d73a511 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 35,46 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
--- 35,53 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel, bool *has_param)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 51,56 ****
--- 58,64 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 59,73 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
  	if (baserel->baserestrictinfo != NIL)
  	{
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
--- 67,91 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
+ 	*has_param = false;
  	if (baserel->baserestrictinfo != NIL)
  	{
+ 		List	   *local_qual = NIL;
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 76,81 ****
--- 94,113 ----
  			List		   *attrs;
  
  			/*
+ 			 * Determine whether the qual can be pushed down or not.  If a qual
+ 			 * can be pushed down and it contains external param, tell that to
+ 			 * caller in order to fall back to fixed costs.
+ 			 */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 			{
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 				if (contain_ext_param((Node*) ri->clause))
+ 					*has_param = true;
+ 			}
+ 			else
+ 				local_qual = lappend(local_qual, ri);
+ 
+ 			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
  			 * SELECT clause of remote query.  We can ignore attributes
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 87,92 ****
--- 119,130 ----
  									PVC_RECURSE_PLACEHOLDERS);
  			attr_used = list_union(attr_used, attrs);
  		}
+ 
+ 		/*
+ 		 * Remove pushed down qualifiers from baserestrictinfo to avoid
+ 		 * redundant evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
  	}
  
  	/*
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 204,210 ****
--- 242,472 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	Oid		func;
+ 
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	/*
+ 	 * If function used by the expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	func = exprFunction(node);
+ 	if (func != InvalidOid && !is_builtin(func))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 		case T_FuncExpr:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index 7fe20e7..1c027ad 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 229,240 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 229,240 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: (((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 342,361 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- ===================================================================
  -- parameterized queries
--- 342,359 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
! (2 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
! (2 rows)
  
  -- ===================================================================
  -- parameterized queries
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 363,379 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 361,374 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (5 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 390,410 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 385,404 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c4) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st1(101, 101);
*** 421,441 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 415,434 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c5) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st3(20, 30);
*** 452,503 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- cleanup
  DEALLOCATE st1;
--- 445,490 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  -- cleanup
  DEALLOCATE st1;
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index 4e2ce84..5480686 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
*************** static void estimate_costs(PlannerInfo *
*** 123,130 ****
  static void execute_query(ForeignScanState *node);
  static PGresult *fetch_result(ForeignScanState *node);
  static void store_result(ForeignScanState *node, PGresult *res);
- static bool contain_ext_param(Node *clause);
- static bool contain_ext_param_walker(Node *node, void *context);
  
  /* Exported functions, but not written in pgsql_fdw.h. */
  void _PG_init(void);
--- 123,128 ----
*************** pgsqlPlanForeignScan(Oid foreigntableid,
*** 194,207 ****
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
! 	sql = deparseSql(foreigntableid, root, baserel);
  	table = GetForeignTable(foreigntableid);
  	server = GetForeignServer(table->serverid);
! 	estimate_costs(root, baserel, sql, server->serverid,
! 				   &fdwplan->startup_cost, &fdwplan->total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
--- 192,222 ----
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
+ 	bool			has_param;
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
! 	sql = deparseSql(foreigntableid, root, baserel, &has_param);
  	table = GetForeignTable(foreigntableid);
  	server = GetForeignServer(table->serverid);
! 
! 	/*
! 	 * If the baserestrictinfo contains any Param node with paramkind
! 	 * PARAM_EXTERNAL as part of push-down-able condition, we need to
! 	 * groundless fixed costs because we can't get actual parameter values
! 	 * here, so we use fixed and large costs as second best so that planner
! 	 * tend to choose custom plan.
! 	 *
! 	 * See comments in plancache.c for details of custom plan.
! 	 */
! 	if (has_param)
! 	{
! 		fdwplan->startup_cost = CONNECTION_COSTS;
! 		fdwplan->total_cost = 10000;	/* groundless large costs */
! 	}
! 	else
! 		estimate_costs(root, baserel, sql, server->serverid,
! 					   &fdwplan->startup_cost, &fdwplan->total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
*************** estimate_costs(PlannerInfo *root, RelOpt
*** 547,553 ****
  			   const char *sql, Oid serverid,
  			   Cost *startup_cost, Cost *total_cost)
  {
- 	ListCell	   *lc;
  	ForeignServer  *server;
  	UserMapping	   *user;
  	PGconn		   *conn = NULL;
--- 562,567 ----
*************** estimate_costs(PlannerInfo *root, RelOpt
*** 558,584 ****
  	int				n;
  
  	/*
- 	 * If the baserestrictinfo contains any Param node with paramkind
- 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
- 	 * simple SELECT statement.  However, we can't get actual parameter values
- 	 * here, so we use fixed and large costs as second best so that planner
- 	 * tend to choose custom plan.
- 	 *
- 	 * See comments in plancache.c for details of custom plan.
- 	 */
- 	foreach(lc, baserel->baserestrictinfo)
- 	{
- 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
- 		if (contain_ext_param((Node *) rs->clause))
- 		{
- 			*startup_cost = CONNECTION_COSTS;
- 			*total_cost = 10000;	/* groundless large costs */
- 
- 			return;
- 		}
- 	}
- 
- 	/*
  	 * Get connection to the foreign server.  Connection manager would
  	 * establish new connection if necessary.
  	 */
--- 572,577 ----
*************** store_result(ForeignScanState *node, PGr
*** 849,885 ****
  
  	tuplestore_donestoring(festate->tuples);
  }
- 
- /*
-  * contain_ext_param
-  *	  Recursively search for Param nodes within a clause.
-  *
-  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
-  *	  found.
-  *
-  * This does not descend into subqueries, and so should be used only after
-  * reduction of sublinks to subplans, or in contexts where it's known there
-  * are no subqueries.  There mustn't be outer-aggregate references either.
-  *
-  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
-  */
- static bool
- contain_ext_param(Node *clause)
- {
- 	return contain_ext_param_walker(clause, NULL);
- }
- 
- static bool
- contain_ext_param_walker(Node *node, void *context)
- {
- 	if (node == NULL)
- 		return false;
- 	if (IsA(node, Param))
- 	{
- 		Param	   *param = (Param *) node;
- 
- 		if (param->paramkind == PARAM_EXTERN)
- 			return true;		/* abort the tree traversal and return true */
- 	}
- 	return expression_tree_walker(node, contain_ext_param_walker, context);
- }
--- 842,844 ----
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index f6394ce..690d58b 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
*************** int ExtractConnectionOptions(List *defel
*** 23,28 ****
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
  
  #endif /* PGSQL_FDW_H */
--- 23,31 ----
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid,
! 				 PlannerInfo *root,
! 				 RelOptInfo *baserel,
! 				 bool *has_param);
  
  #endif /* PGSQL_FDW_H */
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index c9d5d8f..df2e7f6 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 234,245 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
!    Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
! (3 rows)
  </synopsis>
   </sect2>
  
--- 234,244 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! ------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8861.66 rows=518 width=8)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
! (2 rows)
  </synopsis>
   </sect2>
  
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 51459c4..c017d6b 100644
*** a/src/backend/nodes/nodeFuncs.c
--- b/src/backend/nodes/nodeFuncs.c
*************** leftmostLoc(int loc1, int loc2)
*** 1405,1410 ****
--- 1405,1449 ----
  		return Min(loc1, loc2);
  }
  
+ /*
+  *	exprFunction -
+  *	  returns the Oid of the function used by the expression.
+  *
+  * Result is InvalidOid if the node type doesn't store this information.
+  */
+ Oid
+ exprFunction(const Node *expr)
+ {
+ 	Oid			func;
+ 
+ 	if (!expr)
+ 		return InvalidOid;
+ 
+ 	switch (nodeTag(expr))
+ 	{
+ 		case T_Aggref:
+ 			func = ((const Aggref *) expr)->aggfnoid;
+ 			break;
+ 		case T_WindowFunc:
+ 			func = ((const WindowFunc *) expr)->winfnoid;
+ 			break;
+ 		case T_FuncExpr:
+ 			func = ((const FuncExpr *) expr)->funcid;
+ 			break;
+ 		case T_OpExpr:
+ 			func = ((const OpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			func = ((const ScalarArrayOpExpr *) expr)->opfuncid;
+ 			break;
+ 		case T_ArrayCoerceExpr:
+ 			func = ((const ArrayCoerceExpr *) expr)->elemfuncid;
+ 			break;
+ 		default:
+ 			func = InvalidOid;
+ 	}
+ 	return func;
+ }
  
  /*
   * Standard expression-tree walking support
diff --git a/src/include/nodes/nodeFuncs.h b/src/include/nodes/nodeFuncs.h
index def4f31..a3ebe5c 100644
*** a/src/include/nodes/nodeFuncs.h
--- b/src/include/nodes/nodeFuncs.h
*************** extern void exprSetInputCollation(Node *
*** 38,43 ****
--- 38,45 ----
  
  extern int	exprLocation(const Node *expr);
  
+ extern Oid	exprFunction(const Node *expr);
+ 
  extern bool expression_tree_walker(Node *node, bool (*walker) (),
  											   void *context);
  extern Node *expression_tree_mutator(Node *node, Node *(*mutator) (),

*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 25,30 ****
--- 25,31 ----
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
  #include "utils/rel.h"
  #include "utils/syscache.h"
  
***************
*** 93,99 **** PG_FUNCTION_INFO_V1(file_fdw_validator);
  /*
   * FDW callback routines
   */
! static FdwPlan *filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel);
  static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
--- 94,100 ----
  /*
   * FDW callback routines
   */
! static void filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel);
  static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
***************
*** 406,432 **** get_file_fdw_attribute_options(Oid relid)
  
  /*
   * filePlanForeignScan
!  *		Create a FdwPlan for a scan on the foreign table
   */
! static FdwPlan *
  filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel)
  {
  	FdwPlan    *fdwplan;
  	char	   *filename;
  	List	   *options;
  
  	/* Fetch options --- we only need filename at this point */
  	fileGetOptions(foreigntableid, &filename, &options);
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
  	estimate_costs(root, baserel, filename,
  				   &fdwplan->startup_cost, &fdwplan->total_cost);
- 	fdwplan->fdw_private = NIL; /* not used */
  
! 	return fdwplan;
  }
  
  /*
--- 407,447 ----
  
  /*
   * filePlanForeignScan
!  *		Create the (single) path for a scan on the foreign table
   */
! static void
  filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel)
  {
+ 	ForeignPath *pathnode = makeNode(ForeignPath);
  	FdwPlan    *fdwplan;
  	char	   *filename;
  	List	   *options;
  
+ 	pathnode->path.pathtype = T_ForeignScan;
+ 	pathnode->path.parent = baserel;
+ 	pathnode->path.pathkeys = NIL;		/* result is always unordered */
+ 	pathnode->path.required_outer = NULL;
+ 	pathnode->path.param_clauses = NIL;
+ 
  	/* Fetch options --- we only need filename at this point */
  	fileGetOptions(foreigntableid, &filename, &options);
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
+ 	fdwplan->fdw_private = NIL;			/* not used */
  	estimate_costs(root, baserel, filename,
  				   &fdwplan->startup_cost, &fdwplan->total_cost);
  
! 	pathnode->fdwplan = fdwplan;
! 
! 	/* Use costs estimated by FDW */
! 	pathnode->path.rows = baserel->rows;
! 	pathnode->path.startup_cost = fdwplan->startup_cost;
! 	pathnode->path.total_cost = fdwplan->total_cost;
! 
! 	add_path(baserel, (Path *) pathnode);
  }
  
  /*
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
***************
*** 88,108 ****
  
      <para>
  <programlisting>
! FdwPlan *
  PlanForeignScan (Oid foreigntableid,
                   PlannerInfo *root,
                   RelOptInfo *baserel);
  </programlisting>
  
!      Plan a scan on a foreign table. This is called when a query is planned.
       <literal>foreigntableid</> is the <structname>pg_class</> OID of the
       foreign table.  <literal>root</> is the planner's global information
       about the query, and <literal>baserel</> is the planner's information
       about this table.
!      The function must return a palloc'd struct that contains cost estimates
!      plus any FDW-private information that is needed to execute the foreign
!      scan at a later time.  (Note that the private information must be
!      represented in a form that <function>copyObject</> knows how to copy.)
      </para>
  
      <para>
--- 88,114 ----
  
      <para>
  <programlisting>
! void
  PlanForeignScan (Oid foreigntableid,
                   PlannerInfo *root,
                   RelOptInfo *baserel);
  </programlisting>
  
!      Create the access paths for a scan on a foreign table. This is called
!      when a query is planned.
       <literal>foreigntableid</> is the <structname>pg_class</> OID of the
       foreign table.  <literal>root</> is the planner's global information
       about the query, and <literal>baserel</> is the planner's information
       about this table.
!      The function must generate at least one access path for a scan on the
!      foreign table and call <function>add_path</> to add the access path to
!      <literal>baserel-&gt;pathlist</>. The function may generate multiple
!      access paths for a scan on the foreign table and add them to
!      <literal>baserel-&gt;pathlist</>. Each access path generated should
!      contain cost estimates plus any FDW-private information that is needed
!      to execute the foreign scan at a later time.
!      (Note that the private information must be represented in a form that
!      <function>copyObject</> knows how to copy.)
      </para>
  
      <para>
*** a/src/backend/optimizer/path/allpaths.c
--- b/src/backend/optimizer/path/allpaths.c
***************
*** 399,411 **** set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  
  /*
   * set_foreign_pathlist
!  *		Build the (single) access path for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
! 	/* Generate appropriate path */
! 	add_path(rel, (Path *) create_foreignscan_path(root, rel));
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
--- 399,411 ----
  
  /*
   * set_foreign_pathlist
!  *		Build one or more access paths for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
! 	/* Generate appropriate paths */
! 	create_foreignscan_path(root, rel);
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
*** a/src/backend/optimizer/util/pathnode.c
--- b/src/backend/optimizer/util/pathnode.c
***************
*** 1764,1803 **** create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel)
  
  /*
   * create_foreignscan_path
!  *	  Creates a path corresponding to a scan of a foreign table,
!  *	  returning the pathnode.
   */
! ForeignPath *
  create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel)
  {
- 	ForeignPath *pathnode = makeNode(ForeignPath);
  	RangeTblEntry *rte;
  	FdwRoutine *fdwroutine;
- 	FdwPlan    *fdwplan;
- 
- 	pathnode->path.pathtype = T_ForeignScan;
- 	pathnode->path.parent = rel;
- 	pathnode->path.pathkeys = NIL;		/* result is always unordered */
- 	pathnode->path.required_outer = NULL;
- 	pathnode->path.param_clauses = NIL;
  
  	/* Get FDW's callback info */
  	rte = planner_rt_fetch(rel->relid, root);
  	fdwroutine = GetFdwRoutineByRelId(rte->relid);
  
  	/* Let the FDW do its planning */
! 	fdwplan = fdwroutine->PlanForeignScan(rte->relid, root, rel);
! 	if (fdwplan == NULL || !IsA(fdwplan, FdwPlan))
! 		elog(ERROR, "foreign-data wrapper PlanForeignScan function for relation %u did not return an FdwPlan struct",
! 			 rte->relid);
! 	pathnode->fdwplan = fdwplan;
! 
! 	/* use costs estimated by FDW */
! 	pathnode->path.rows = rel->rows;
! 	pathnode->path.startup_cost = fdwplan->startup_cost;
! 	pathnode->path.total_cost = fdwplan->total_cost;
! 
! 	return pathnode;
  }
  
  /*
--- 1764,1784 ----
  
  /*
   * create_foreignscan_path
!  *	  Creates one or more paths corresponding to a scan of a foreign table,
!  *	  returning void.
   */
! void
  create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel)
  {
  	RangeTblEntry *rte;
  	FdwRoutine *fdwroutine;
  
  	/* Get FDW's callback info */
  	rte = planner_rt_fetch(rel->relid, root);
  	fdwroutine = GetFdwRoutineByRelId(rte->relid);
  
  	/* Let the FDW do its planning */
! 	fdwroutine->PlanForeignScan(rte->relid, root, rel);
  }
  
  /*
*** a/src/include/foreign/fdwapi.h
--- b/src/include/foreign/fdwapi.h
***************
*** 52,58 **** typedef struct FdwPlan
   * Callback function signatures --- see fdwhandler.sgml for more info.
   */
  
! typedef FdwPlan *(*PlanForeignScan_function) (Oid foreigntableid,
  														  PlannerInfo *root,
  														RelOptInfo *baserel);
  
--- 52,58 ----
   * Callback function signatures --- see fdwhandler.sgml for more info.
   */
  
! typedef void (*PlanForeignScan_function) (Oid foreigntableid,
  														  PlannerInfo *root,
  														RelOptInfo *baserel);
  
*** a/src/include/optimizer/pathnode.h
--- b/src/include/optimizer/pathnode.h
***************
*** 68,74 **** extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
! extern ForeignPath *create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel);
  
  extern Relids calc_nestloop_required_outer(Path *outer_path, Path *inner_path);
  extern Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path);
--- 68,74 ----
  extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
! extern void create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel);
  
  extern Relids calc_nestloop_required_outer(Path *outer_path, Path *inner_path);
  extern Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path);

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 46394a8..a522e36 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 26,32 ****
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 26,32 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 345,398 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 345,373 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..d809cac 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 235,238 ****
--- 235,392 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum, const char *optname);
+ </programlisting>
+ 
+      This function returns a copied string (created in current memory context)
+      of the value of a FDW option with given name which is set on a object with
+      given oid and attribute number.  This function ignores catalogs if invalid
+      identifir is given for it.
+ 
+      <itemizedlist>
+       <listitem>
+        <para>
+         If attnum is <literal>InvalidAttrNumber</literal> or relid is
+         <literal>Invalidoid</literal>, <structname>pg_attribute</structname> is
+         ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If relid is <literal>InvalidOid</literal>,
+         <structname>pg_foreign_table</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If both serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_server</structname> is ignored.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         If all of fdwid, serverid and relid are <literal>InvalidOid</literal>,
+         <structname>pg_foreign_data_wrapper</structname> is ignored.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+ 
+     <para>
+      If the option with given name is set in multiple object level, the one in
+      the finest-grained object is used; e.g. priority is given to user mappings 
+      over than foreign servers.
+      This function would be useful when you know which option is needed but you
+      don't know where it is set.  If you already know the source object, it
+      would be more efficient to use object retrieval functions.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index c4c2a61..8e98f0f 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
*************** GetForeignTable(Oid relid)
*** 248,253 ****
--- 248,378 ----
  
  
  /*
+  * If an option entry which matches the given name was found in the given
+  * list, returns a copy of arg string, otherwise returns NULL.
+  */
+ static char *
+ get_options_value(List *options, const char *optname)
+ {
+ 	ListCell   *lc;
+ 
+ 	/* Find target option from the list. */
+ 	foreach (lc, options)
+ 	{
+ 		DefElem	   *def = lfirst(lc);
+ 
+ 		if (strcmp(def->defname, optname) == 0)
+ 			return pstrdup(strVal(def->arg));
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ /*
+  * Returns a copy of the value of specified option with searching the option
+  * from appropriate catalog.  If an option was stored in multiple object
+  * levels, one in the finest-grained object level is used; lookup order is:
+  *   1) pg_attribute (only when both attnum and relid are valid)
+  *   2) pg_foreign_table (only when relid is valid)
+  *   3) pg_user_mapping (only when serverid or relid is valid)
+  *   4) pg_foreign_server (only when serverid or relid is valid)
+  *   5) pg_foreign_data_wrapper (only when fdwid or serverid or relid is valid)
+  * This priority rule would be useful in most cases using FDW options.
+  *
+  * If attnum was InvalidAttrNumber, we don't retrieve FDW optiosn from
+  * pg_attribute.attfdwoptions.
+  */
+ char *
+ GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid, AttrNumber attnum,
+ 				  const char *optname)
+ {
+ 	ForeignTable   *table = NULL;
+ 	UserMapping	   *user = NULL;
+ 	ForeignServer  *server = NULL;
+ 	ForeignDataWrapper  *wrapper = NULL;
+ 	char		   *value;
+ 
+ 	/* Do we need to search pg_attribute? */
+ 	if (attnum != InvalidAttrNumber && relid != InvalidOid)
+ 	{
+ 		value = get_options_value(GetForeignColumnOptions(relid, attnum),
+ 								  optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_table? */
+ 	if (relid != InvalidOid)
+ 	{
+ 		table = GetForeignTable(relid);
+ 		value = get_options_value(table->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		serverid = table->serverid;
+ 	}
+ 
+ 	/* Do we need to search pg_user_mapping and pg_foreign_server? */
+ 	if (serverid != InvalidOid)
+ 	{
+ 		user = GetUserMapping(GetOuterUserId(), serverid);
+ 		value = get_options_value(user->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		server = GetForeignServer(serverid);
+ 		value = get_options_value(server->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 
+ 		fdwid = server->fdwid;
+ 	}
+ 
+ 	/* Do we need to search pg_foreign_data_wrapper? */
+ 	if (fdwid != InvalidOid)
+ 	{
+ 		wrapper = GetForeignDataWrapper(fdwid);
+ 		value = get_options_value(wrapper->options, optname);
+ 		if (value != NULL)
+ 			return value;
+ 	}
+ 
+ 	return NULL;
+ }
+ 
+ 
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
+ 
+ /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
   * to get its FdwRoutine struct.
   */
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 191122d..e25b871 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,83 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern char *GetFdwOptionValue(Oid fdwid, Oid serverid, Oid relid,
+ 							AttrNumber attnum, const char *optname);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...48a5f1e .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,553 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+ 			break;
+ 		case XACT_READ_COMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+ 			break;
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...7ca2767 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,210 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 *
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 												attr, "colname");
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...7fe20e7 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,546 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                   List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                     FDW Options                                                                                                                                                                     | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                      | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...f0fd1fe .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,246 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...b92258a .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,895 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 */
+ 	res = fetch_result(node);
+ 	PG_TRY();
+ 	{
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* Reset cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* Close cursor */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	conn = festate->conn;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 	res = PQexec(conn, sql);
+ 	PG_TRY();
+ 	{
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Execute remote query with parameters.
+ 	 */
+ 	conn = festate->conn;
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...42d26fd .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,231 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...678e0c6 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,253 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    The transaction isolation level used for remote transaction is same as
+    local transaction.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9ad54c5..c2a5a7b 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 2c331ce..dc6932a 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 648,653 ****
--- 648,654 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index 7ca2767..044f057 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 35,46 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
--- 35,53 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel, bool *has_param)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 51,56 ****
--- 58,64 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 59,73 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
  	if (baserel->baserestrictinfo != NIL)
  	{
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
--- 67,91 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
+ 	*has_param = false;
  	if (baserel->baserestrictinfo != NIL)
  	{
+ 		List	   *local_qual = NIL;
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 76,81 ****
--- 94,113 ----
  			List		   *attrs;
  
  			/*
+ 			 * Determine whether the qual can be pushed down or not.  If a qual
+ 			 * can be pushed down and it contains external param, tell that to
+ 			 * caller in order to fall back to fixed costs.
+ 			 */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 			{
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 				if (contain_ext_param((Node*) ri->clause))
+ 					*has_param = true;
+ 			}
+ 			else
+ 				local_qual = lappend(local_qual, ri);
+ 
+ 			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
  			 * SELECT clause of remote query.  We can ignore attributes
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 87,92 ****
--- 119,130 ----
  									PVC_RECURSE_PLACEHOLDERS);
  			attr_used = list_union(attr_used, attrs);
  		}
+ 
+ 		/*
+ 		 * Remove pushed down qualifiers from baserestrictinfo to avoid
+ 		 * redundant evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
  	}
  
  	/*
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 204,210 ****
--- 242,473 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		/*
+ 		 * If function used by the expression is not built-in, it can't be
+ 		 * pushed down because it might has incompatible semantics on remote
+ 		 * side.
+ 		 */
+ 		case T_FuncExpr:
+ 			{
+ 				FuncExpr	   *fe = (FuncExpr *) node;
+ 				if (!is_builtin(fe->funcid))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index 7fe20e7..1c027ad 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 229,240 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 229,240 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: (((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 342,361 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- ===================================================================
  -- parameterized queries
--- 342,359 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
! (2 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
! (2 rows)
  
  -- ===================================================================
  -- parameterized queries
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 363,379 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 361,374 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (5 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 390,410 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 385,404 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c4) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st1(101, 101);
*** 421,441 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 415,434 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c5) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st3(20, 30);
*** 452,503 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- cleanup
  DEALLOCATE st1;
--- 445,490 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  -- cleanup
  DEALLOCATE st1;
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index b92258a..3f35b05 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
*************** static void estimate_costs(PlannerInfo *
*** 123,130 ****
  static void execute_query(ForeignScanState *node);
  static PGresult *fetch_result(ForeignScanState *node);
  static void store_result(ForeignScanState *node, PGresult *res);
- static bool contain_ext_param(Node *clause);
- static bool contain_ext_param_walker(Node *node, void *context);
  
  /* Exported functions, but not written in pgsql_fdw.h. */
  void _PG_init(void);
--- 123,128 ----
*************** pgsqlPlanForeignScan(Oid foreigntableid,
*** 194,207 ****
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
! 	sql = deparseSql(foreigntableid, root, baserel);
  	table = GetForeignTable(foreigntableid);
  	server = GetForeignServer(table->serverid);
! 	estimate_costs(root, baserel, sql, server->serverid,
! 				   &fdwplan->startup_cost, &fdwplan->total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
--- 192,222 ----
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
+ 	bool			has_param;
  
  	/* Construct FdwPlan with cost estimates */
  	fdwplan = makeNode(FdwPlan);
! 	sql = deparseSql(foreigntableid, root, baserel, &has_param);
  	table = GetForeignTable(foreigntableid);
  	server = GetForeignServer(table->serverid);
! 
! 	/*
! 	 * If the baserestrictinfo contains any Param node with paramkind
! 	 * PARAM_EXTERNAL as part of push-down-able condition, we need to
! 	 * groundless fixed costs because we can't get actual parameter values
! 	 * here, so we use fixed and large costs as second best so that planner
! 	 * tend to choose custom plan.
! 	 *
! 	 * See comments in plancache.c for details of custom plan.
! 	 */
! 	if (has_param)
! 	{
! 		fdwplan->startup_cost = CONNECTION_COSTS;
! 		fdwplan->total_cost = 10000;	/* groundless large costs */
! 	}
! 	else
! 		estimate_costs(root, baserel, sql, server->serverid,
! 					   &fdwplan->startup_cost, &fdwplan->total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
*************** estimate_costs(PlannerInfo *root, RelOpt
*** 550,556 ****
  			   const char *sql, Oid serverid,
  			   Cost *startup_cost, Cost *total_cost)
  {
- 	ListCell	   *lc;
  	ForeignServer  *server;
  	UserMapping	   *user;
  	PGconn		   *conn = NULL;
--- 565,570 ----
*************** estimate_costs(PlannerInfo *root, RelOpt
*** 561,587 ****
  	int				n;
  
  	/*
- 	 * If the baserestrictinfo contains any Param node with paramkind
- 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
- 	 * simple SELECT statement.  However, we can't get actual parameter values
- 	 * here, so we use fixed and large costs as second best so that planner
- 	 * tend to choose custom plan.
- 	 *
- 	 * See comments in plancache.c for details of custom plan.
- 	 */
- 	foreach(lc, baserel->baserestrictinfo)
- 	{
- 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
- 		if (contain_ext_param((Node *) rs->clause))
- 		{
- 			*startup_cost = CONNECTION_COSTS;
- 			*total_cost = 10000;	/* groundless large costs */
- 
- 			return;
- 		}
- 	}
- 
- 	/*
  	 * Get connection to the foreign server.  Connection manager would
  	 * establish new connection if necessary.
  	 */
--- 575,580 ----
*************** store_result(ForeignScanState *node, PGr
*** 859,895 ****
  
  	tuplestore_donestoring(festate->tuples);
  }
- 
- /*
-  * contain_ext_param
-  *	  Recursively search for Param nodes within a clause.
-  *
-  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
-  *	  found.
-  *
-  * This does not descend into subqueries, and so should be used only after
-  * reduction of sublinks to subplans, or in contexts where it's known there
-  * are no subqueries.  There mustn't be outer-aggregate references either.
-  *
-  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
-  */
- static bool
- contain_ext_param(Node *clause)
- {
- 	return contain_ext_param_walker(clause, NULL);
- }
- 
- static bool
- contain_ext_param_walker(Node *node, void *context)
- {
- 	if (node == NULL)
- 		return false;
- 	if (IsA(node, Param))
- 	{
- 		Param	   *param = (Param *) node;
- 
- 		if (param->paramkind == PARAM_EXTERN)
- 			return true;		/* abort the tree traversal and return true */
- 	}
- 	return expression_tree_walker(node, contain_ext_param_walker, context);
- }
--- 852,854 ----
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index f6394ce..690d58b 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
*************** int ExtractConnectionOptions(List *defel
*** 23,28 ****
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
  
  #endif /* PGSQL_FDW_H */
--- 23,31 ----
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid,
! 				 PlannerInfo *root,
! 				 RelOptInfo *baserel,
! 				 bool *has_param);
  
  #endif /* PGSQL_FDW_H */
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index 678e0c6..6a48c60 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 234,245 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
!    Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
! (3 rows)
  </synopsis>
   </sect2>
  
--- 234,244 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! ------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8861.66 rows=518 width=8)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
! (2 rows)
  </synopsis>
   </sect2>
  

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...48a5f1e .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,553 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+ 			break;
+ 		case XACT_READ_COMMITTED:
+ 			sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+ 			break;
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...7ca2767 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,210 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 *
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 												attr, "colname");
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...dfe6351 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,547 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...7e22795 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,247 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ #ifdef USE_SSL
+ 	{"requiressl", ForeignServerRelationId, true},
+ #endif
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ #if defined(KRB5) || defined(ENABLE_GSS) || defined(ENABLE_SSPI)
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ #endif
+ #if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
+ 	{"gsslib", ForeignServerRelationId, true},
+ #endif
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...50f927b .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,907 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdwplan->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdwplan->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 		sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...f257b34 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,232 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...678e0c6 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,253 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    The transaction isolation level used for remote transaction is same as
+    local transaction.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9ad54c5..c2a5a7b 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2161,2166 ****
--- 2161,2189 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 2c331ce..dc6932a 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 648,653 ****
--- 648,654 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 25,30 ****
--- 25,31 ----
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
  #include "utils/rel.h"
  #include "utils/syscache.h"
  
***************
*** 93,99 **** PG_FUNCTION_INFO_V1(file_fdw_validator);
  /*
   * FDW callback routines
   */
! static FdwPlan *filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel);
  static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
--- 94,100 ----
  /*
   * FDW callback routines
   */
! static void filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel);
  static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
***************
*** 406,432 **** get_file_fdw_attribute_options(Oid relid)
  
  /*
   * filePlanForeignScan
!  *		Create a FdwPlan for a scan on the foreign table
   */
! static FdwPlan *
  filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel)
  {
! 	FdwPlan    *fdwplan;
  	char	   *filename;
  	List	   *options;
  
  	/* Fetch options --- we only need filename at this point */
  	fileGetOptions(foreigntableid, &filename, &options);
  
! 	/* Construct FdwPlan with cost estimates */
! 	fdwplan = makeNode(FdwPlan);
  	estimate_costs(root, baserel, filename,
! 				   &fdwplan->startup_cost, &fdwplan->total_cost);
! 	fdwplan->fdw_private = NIL; /* not used */
  
! 	return fdwplan;
  }
  
  /*
--- 407,439 ----
  
  /*
   * filePlanForeignScan
!  *		Create the (single) path for a scan on the foreign table
   */
! static void
  filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel)
  {
! 	ForeignPath *pathnode = makeNode(ForeignPath);
  	char	   *filename;
  	List	   *options;
  
+ 	pathnode->path.pathtype = T_ForeignScan;
+ 	pathnode->path.parent = baserel;
+ 	pathnode->path.pathkeys = NIL;		/* result is always unordered */
+ 	pathnode->path.required_outer = NULL;
+ 	pathnode->path.param_clauses = NIL;
+ 	pathnode->fdw_private = NIL;		/* not used */
+ 
  	/* Fetch options --- we only need filename at this point */
  	fileGetOptions(foreigntableid, &filename, &options);
  
! 	/* Estimate costs of scanning the foreign table */
  	estimate_costs(root, baserel, filename,
! 				   &pathnode->path.startup_cost, &pathnode->path.total_cost);
! 	pathnode->path.rows = baserel->rows;
  
! 	add_path(baserel, (Path *) pathnode);
  }
  
  /*
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
***************
*** 88,108 ****
  
      <para>
  <programlisting>
! FdwPlan *
  PlanForeignScan (Oid foreigntableid,
                   PlannerInfo *root,
                   RelOptInfo *baserel);
  </programlisting>
  
!      Plan a scan on a foreign table. This is called when a query is planned.
       <literal>foreigntableid</> is the <structname>pg_class</> OID of the
       foreign table.  <literal>root</> is the planner's global information
       about the query, and <literal>baserel</> is the planner's information
       about this table.
!      The function must return a palloc'd struct that contains cost estimates
!      plus any FDW-private information that is needed to execute the foreign
!      scan at a later time.  (Note that the private information must be
!      represented in a form that <function>copyObject</> knows how to copy.)
      </para>
  
      <para>
--- 88,114 ----
  
      <para>
  <programlisting>
! void
  PlanForeignScan (Oid foreigntableid,
                   PlannerInfo *root,
                   RelOptInfo *baserel);
  </programlisting>
  
!      Create the access paths for a scan on a foreign table. This is called
!      when a query is planned.
       <literal>foreigntableid</> is the <structname>pg_class</> OID of the
       foreign table.  <literal>root</> is the planner's global information
       about the query, and <literal>baserel</> is the planner's information
       about this table.
!      The function must generate at least one access path for a scan on the
!      foreign table and call <function>add_path</> to add it to
!      <literal>baserel-&gt;pathlist</>.  The function may generate multiple
!      access paths for a scan on the foreign table and add them to
!      <literal>baserel-&gt;pathlist</> using <function>add_path</>.  Each
!      access path generated should contain cost estimates plus any FDW-private
!      information that is needed to execute the foreign scan at a later time.
!      (Note that the private information must be represented in a form that
!      <function>copyObject</> knows how to copy.)
      </para>
  
      <para>
***************
*** 159,167 **** BeginForeignScan (ForeignScanState *node,
       its <structfield>fdw_state</> field is still NULL.  Information about
       the table to scan is accessible through the
       <structname>ForeignScanState</> node (in particular, from the underlying
!      <structname>ForeignScan</> plan node, which contains a pointer to the
!      <structname>FdwPlan</> structure returned by
!      <function>PlanForeignScan</>).
      </para>
  
      <para>
--- 165,172 ----
       its <structfield>fdw_state</> field is still NULL.  Information about
       the table to scan is accessible through the
       <structname>ForeignScanState</> node (in particular, from the underlying
!      <structname>ForeignScan</> plan node, which contains FDW-private
!      information about it provided by <function>PlanForeignScan</>).
      </para>
  
      <para>
***************
*** 228,236 **** EndForeignScan (ForeignScanState *node);
      </para>
  
      <para>
!      The <structname>FdwRoutine</> and <structname>FdwPlan</> struct types
!      are declared in <filename>src/include/foreign/fdwapi.h</>, which see
!      for additional details.
      </para>
  
     </sect1>
--- 233,241 ----
      </para>
  
      <para>
!      The <structname>FdwRoutine</> struct type is declared
!      in <filename>src/include/foreign/fdwapi.h</>, which see for additional
!      details.
      </para>
  
     </sect1>
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
***************
*** 591,611 **** _copyForeignScan(const ForeignScan *from)
  	 * copy remainder of node
  	 */
  	COPY_SCALAR_FIELD(fsSystemCol);
- 	COPY_NODE_FIELD(fdwplan);
- 
- 	return newnode;
- }
- 
- /*
-  * _copyFdwPlan
-  */
- static FdwPlan *
- _copyFdwPlan(const FdwPlan *from)
- {
- 	FdwPlan    *newnode = makeNode(FdwPlan);
- 
- 	COPY_SCALAR_FIELD(startup_cost);
- 	COPY_SCALAR_FIELD(total_cost);
  	COPY_NODE_FIELD(fdw_private);
  
  	return newnode;
--- 591,596 ----
***************
*** 3841,3849 **** copyObject(const void *from)
  		case T_ForeignScan:
  			retval = _copyForeignScan(from);
  			break;
- 		case T_FdwPlan:
- 			retval = _copyFdwPlan(from);
- 			break;
  		case T_Join:
  			retval = _copyJoin(from);
  			break;
--- 3826,3831 ----
*** a/src/backend/nodes/outfuncs.c
--- b/src/backend/nodes/outfuncs.c
***************
*** 558,573 **** _outForeignScan(StringInfo str, const ForeignScan *node)
  	_outScanInfo(str, (const Scan *) node);
  
  	WRITE_BOOL_FIELD(fsSystemCol);
- 	WRITE_NODE_FIELD(fdwplan);
- }
- 
- static void
- _outFdwPlan(StringInfo str, const FdwPlan *node)
- {
- 	WRITE_NODE_TYPE("FDWPLAN");
- 
- 	WRITE_FLOAT_FIELD(startup_cost, "%.2f");
- 	WRITE_FLOAT_FIELD(total_cost, "%.2f");
  	WRITE_NODE_FIELD(fdw_private);
  }
  
--- 558,563 ----
***************
*** 1572,1578 **** _outForeignPath(StringInfo str, const ForeignPath *node)
  
  	_outPathInfo(str, (const Path *) node);
  
! 	WRITE_NODE_FIELD(fdwplan);
  }
  
  static void
--- 1562,1568 ----
  
  	_outPathInfo(str, (const Path *) node);
  
! 	WRITE_NODE_FIELD(fdw_private);
  }
  
  static void
***************
*** 2744,2752 **** _outNode(StringInfo str, const void *obj)
  			case T_ForeignScan:
  				_outForeignScan(str, obj);
  				break;
- 			case T_FdwPlan:
- 				_outFdwPlan(str, obj);
- 				break;
  			case T_Join:
  				_outJoin(str, obj);
  				break;
--- 2734,2739 ----
*** a/src/backend/optimizer/path/allpaths.c
--- b/src/backend/optimizer/path/allpaths.c
***************
*** 399,411 **** set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  
  /*
   * set_foreign_pathlist
!  *		Build the (single) access path for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
! 	/* Generate appropriate path */
! 	add_path(rel, (Path *) create_foreignscan_path(root, rel));
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
--- 399,411 ----
  
  /*
   * set_foreign_pathlist
!  *		Build one or more access paths for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
! 	/* Generate appropriate paths */
! 	create_foreignscan_path(root, rel);
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
*** a/src/backend/optimizer/plan/createplan.c
--- b/src/backend/optimizer/plan/createplan.c
***************
*** 121,127 **** static CteScan *make_ctescan(List *qptlist, List *qpqual,
  static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
  				   Index scanrelid, int wtParam);
  static ForeignScan *make_foreignscan(List *qptlist, List *qpqual,
! 				 Index scanrelid, bool fsSystemCol, FdwPlan *fdwplan);
  static BitmapAnd *make_bitmap_and(List *bitmapplans);
  static BitmapOr *make_bitmap_or(List *bitmapplans);
  static NestLoop *make_nestloop(List *tlist,
--- 121,127 ----
  static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
  				   Index scanrelid, int wtParam);
  static ForeignScan *make_foreignscan(List *qptlist, List *qpqual,
! 				 Index scanrelid, bool fsSystemCol, List *fdw_private);
  static BitmapAnd *make_bitmap_and(List *bitmapplans);
  static BitmapOr *make_bitmap_or(List *bitmapplans);
  static NestLoop *make_nestloop(List *tlist,
***************
*** 1847,1853 **** create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
  								 scan_clauses,
  								 scan_relid,
  								 fsSystemCol,
! 								 best_path->fdwplan);
  
  	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
  
--- 1847,1853 ----
  								 scan_clauses,
  								 scan_relid,
  								 fsSystemCol,
! 								 best_path->fdw_private);
  
  	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
  
***************
*** 3189,3195 **** make_foreignscan(List *qptlist,
  				 List *qpqual,
  				 Index scanrelid,
  				 bool fsSystemCol,
! 				 FdwPlan *fdwplan)
  {
  	ForeignScan *node = makeNode(ForeignScan);
  	Plan	   *plan = &node->scan.plan;
--- 3189,3195 ----
  				 List *qpqual,
  				 Index scanrelid,
  				 bool fsSystemCol,
! 				 List *fdw_private)
  {
  	ForeignScan *node = makeNode(ForeignScan);
  	Plan	   *plan = &node->scan.plan;
***************
*** 3201,3207 **** make_foreignscan(List *qptlist,
  	plan->righttree = NULL;
  	node->scan.scanrelid = scanrelid;
  	node->fsSystemCol = fsSystemCol;
! 	node->fdwplan = fdwplan;
  
  	return node;
  }
--- 3201,3207 ----
  	plan->righttree = NULL;
  	node->scan.scanrelid = scanrelid;
  	node->fsSystemCol = fsSystemCol;
! 	node->fdw_private = fdw_private;
  
  	return node;
  }
*** a/src/backend/optimizer/util/pathnode.c
--- b/src/backend/optimizer/util/pathnode.c
***************
*** 1764,1803 **** create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel)
  
  /*
   * create_foreignscan_path
!  *	  Creates a path corresponding to a scan of a foreign table,
!  *	  returning the pathnode.
   */
! ForeignPath *
  create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel)
  {
- 	ForeignPath *pathnode = makeNode(ForeignPath);
  	RangeTblEntry *rte;
  	FdwRoutine *fdwroutine;
- 	FdwPlan    *fdwplan;
- 
- 	pathnode->path.pathtype = T_ForeignScan;
- 	pathnode->path.parent = rel;
- 	pathnode->path.pathkeys = NIL;		/* result is always unordered */
- 	pathnode->path.required_outer = NULL;
- 	pathnode->path.param_clauses = NIL;
  
  	/* Get FDW's callback info */
  	rte = planner_rt_fetch(rel->relid, root);
  	fdwroutine = GetFdwRoutineByRelId(rte->relid);
  
  	/* Let the FDW do its planning */
! 	fdwplan = fdwroutine->PlanForeignScan(rte->relid, root, rel);
! 	if (fdwplan == NULL || !IsA(fdwplan, FdwPlan))
! 		elog(ERROR, "foreign-data wrapper PlanForeignScan function for relation %u did not return an FdwPlan struct",
! 			 rte->relid);
! 	pathnode->fdwplan = fdwplan;
! 
! 	/* use costs estimated by FDW */
! 	pathnode->path.rows = rel->rows;
! 	pathnode->path.startup_cost = fdwplan->startup_cost;
! 	pathnode->path.total_cost = fdwplan->total_cost;
! 
! 	return pathnode;
  }
  
  /*
--- 1764,1786 ----
  
  /*
   * create_foreignscan_path
!  *	  Creates one or more paths corresponding to a scan of a foreign table,
!  *	  returning void.
   */
! void
  create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel)
  {
  	RangeTblEntry *rte;
  	FdwRoutine *fdwroutine;
  
  	/* Get FDW's callback info */
  	rte = planner_rt_fetch(rel->relid, root);
  	fdwroutine = GetFdwRoutineByRelId(rte->relid);
  
  	/* Let the FDW do its planning */
! 	fdwroutine->PlanForeignScan(rte->relid, root, rel);
! 	if (rel->pathlist == NIL)
! 		elog(ERROR, "could not devise a query plan for the given query");
  }
  
  /*
*** a/src/include/foreign/fdwapi.h
--- b/src/include/foreign/fdwapi.h
***************
*** 20,58 **** struct ExplainState;
  
  
  /*
-  * FdwPlan is the information returned to the planner by PlanForeignScan.
-  */
- typedef struct FdwPlan
- {
- 	NodeTag		type;
- 
- 	/*
- 	 * Cost estimation info. The startup_cost is time before retrieving the
- 	 * first row, so it should include costs of connecting to the remote host,
- 	 * sending over the query, etc.  Note that PlanForeignScan also ought to
- 	 * set baserel->rows and baserel->width if it can produce any usable
- 	 * estimates of those values.
- 	 */
- 	Cost		startup_cost;	/* cost expended before fetching any tuples */
- 	Cost		total_cost;		/* total cost (assuming all tuples fetched) */
- 
- 	/*
- 	 * FDW private data, which will be available at execution time.
- 	 *
- 	 * Note that everything in this list must be copiable by copyObject(). One
- 	 * way to store an arbitrary blob of bytes is to represent it as a bytea
- 	 * Const.  Usually, though, you'll be better off choosing a representation
- 	 * that can be dumped usefully by nodeToString().
- 	 */
- 	List	   *fdw_private;
- } FdwPlan;
- 
- 
- /*
   * Callback function signatures --- see fdwhandler.sgml for more info.
   */
  
! typedef FdwPlan *(*PlanForeignScan_function) (Oid foreigntableid,
  														  PlannerInfo *root,
  														RelOptInfo *baserel);
  
--- 20,29 ----
  
  
  /*
   * Callback function signatures --- see fdwhandler.sgml for more info.
   */
  
! typedef void (*PlanForeignScan_function) (Oid foreigntableid,
  														  PlannerInfo *root,
  														RelOptInfo *baserel);
  
*** a/src/include/nodes/nodes.h
--- b/src/include/nodes/nodes.h
***************
*** 62,68 **** typedef enum NodeTag
  	T_CteScan,
  	T_WorkTableScan,
  	T_ForeignScan,
- 	T_FdwPlan,
  	T_Join,
  	T_NestLoop,
  	T_MergeJoin,
--- 62,67 ----
*** a/src/include/nodes/plannodes.h
--- b/src/include/nodes/plannodes.h
***************
*** 468,475 **** typedef struct ForeignScan
  {
  	Scan		scan;
  	bool		fsSystemCol;	/* true if any "system column" is needed */
! 	/* use struct pointer to avoid including fdwapi.h here */
! 	struct FdwPlan *fdwplan;
  } ForeignScan;
  
  
--- 468,474 ----
  {
  	Scan		scan;
  	bool		fsSystemCol;	/* true if any "system column" is needed */
! 	List	   *fdw_private;
  } ForeignScan;
  
  
*** a/src/include/nodes/relation.h
--- b/src/include/nodes/relation.h
***************
*** 794,805 **** typedef struct TidPath
  
  /*
   * ForeignPath represents a scan of a foreign table
   */
  typedef struct ForeignPath
  {
  	Path		path;
! 	/* use struct pointer to avoid including fdwapi.h here */
! 	struct FdwPlan *fdwplan;
  } ForeignPath;
  
  /*
--- 794,810 ----
  
  /*
   * ForeignPath represents a scan of a foreign table
+  *
+  * fdw_private is a list of FDW private data, which will be available at
+  * execution time.  Note that everything in this list must be copiable
+  * by copyObject().  One way to store an arbitrary blob of bytes is to
+  * represent it as a bytea Const.  Usually, though, you'll be better off
+  * choosing a representation that can be dumped usefully by nodeToString().
   */
  typedef struct ForeignPath
  {
  	Path		path;
! 	List	   *fdw_private;
  } ForeignPath;
  
  /*
*** a/src/include/optimizer/pathnode.h
--- b/src/include/optimizer/pathnode.h
***************
*** 68,74 **** extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
! extern ForeignPath *create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel);
  
  extern Relids calc_nestloop_required_outer(Path *outer_path, Path *inner_path);
  extern Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path);
--- 68,74 ----
  extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
  extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
! extern void create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel);
  
  extern Relids calc_nestloop_required_outer(Path *outer_path, Path *inner_path);
  extern Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path);

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...4f3e5a6 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,549 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 		case XACT_READ_COMMITTED:
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...7ca2767 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,210 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 *
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 												attr, "colname");
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...0e2289c .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,547 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, requiressl, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...13035c1 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,241 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ 	{"requiressl", ForeignServerRelationId, true},
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ 	{"gsslib", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...50f927b .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,907 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private items stored in FdwPlan.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	FdwPlan	   *fdwplan;		/* FDW-specific planning information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static FdwPlan *pgsqlPlanForeignScan(Oid foreigntableid,
+ 									 PlannerInfo *root,
+ 									 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create a FdwPlan for a scan on the foreign table
+  */
+ static FdwPlan *
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	FdwPlan		   *fdwplan;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/* Construct FdwPlan with cost estimates */
+ 	fdwplan = makeNode(FdwPlan);
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &fdwplan->startup_cost, &fdwplan->total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Store FDW private information into FdwPlan */
+ 	fdwplan->fdw_private = fdw_private;
+ 
+ 	return fdwplan;
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	FdwPlan	   *fdwplan;
+ 	char	   *sql;
+ 
+ 	fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 	sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdwplan->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdwplan->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ListCell	   *lc;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL, we need result of EXPLAIN for EXECUTE statement, not for
+ 	 * simple SELECT statement.  However, we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
+ 	 */
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo	   *rs = (RestrictInfo *) lfirst(lc);
+ 		if (contain_ext_param((Node *) rs->clause))
+ 		{
+ 			*startup_cost = CONNECTION_COSTS;
+ 			*total_cost = 10000;	/* groundless large costs */
+ 
+ 			return;
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	FdwPlan		   *fdwplan;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdwplan = ((ForeignScan *) node->ss.ps.plan)->fdwplan;
+ 		sql = strVal(list_nth(fdwplan->fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdwplan->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...f257b34 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,232 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...30fa7f5 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,261 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    If isolation level of local transaction is <literal>SERIALIZABLE</literal>,
+    <literal>SERIALIZABLE</literal> is used for remote transaction.  Otherwise,
+    if isolation level of local transaction is one of
+    <literal>READ UNCOMMITTED</literal>, <literal>READ COMMITTED</literal> or
+    <literal>REPEATABLE READ</literal>, then <literal>REPEATABLE READ</literal>
+    is used for remote transaction.
+    <literal>READ UNCOMMITTED</literal> and <literal>READ COMMITTED</literal>
+    are never used for remote transaction, because even
+    <literal>READ COMMITTED</literal> transaction might produce inconsistent
+    results, if remote data have been updated between two remote queries.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 64ba8ec..94b2ea9 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2181,2186 ****
--- 2181,2209 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index fe253bc..8ad4d48 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 649,654 ****
--- 649,655 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/dblink/Makefile b/contrib/dblink/Makefile
index ac63748..a27db88 100644
*** a/contrib/dblink/Makefile
--- b/contrib/dblink/Makefile
*************** SHLIB_LINK = $(libpq)
*** 7,13 ****
  SHLIB_PREREQS = submake-libpq
  
  EXTENSION = dblink
! DATA = dblink--1.0.sql dblink--unpackaged--1.0.sql
  
  REGRESS = dblink
  
--- 7,13 ----
  SHLIB_PREREQS = submake-libpq
  
  EXTENSION = dblink
! DATA = dblink--1.1.sql dblink--1.0--1.1.sql dblink--unpackaged--1.0.sql
  
  REGRESS = dblink
  
diff --git a/contrib/dblink/dblink--1.0--1.1.sql b/contrib/dblink/dblink--1.0--1.1.sql
index ...3dd02a0 .
*** a/contrib/dblink/dblink--1.0--1.1.sql
--- b/contrib/dblink/dblink--1.0--1.1.sql
***************
*** 0 ****
--- 1,17 ----
+ /* contrib/dblink/dblink--1.0--1.1.sql */
+ 
+ -- complain if script is sourced in psql, rather than via ALTER EXTENSION
+ \echo Use "ALTER EXTENSION dblink UPDATE" to load this file. \quit
+ 
+ /* First we have to create validator function */
+ CREATE FUNCTION dblink_fdw_validator(
+     options text[],
+     catalog oid
+ )
+ RETURNS boolean
+ AS 'MODULE_PATHNAME', 'dblink_fdw_validator'
+ LANGUAGE C STRICT;
+ 
+ /* Then we add the validator */
+ ALTER EXTENSION dblink ADD FUNCTION dblink_fdw_validator(text[], oid);
+ 
diff --git a/contrib/dblink/dblink--1.1.sql b/contrib/dblink/dblink--1.1.sql
index ...ec02498 .
*** a/contrib/dblink/dblink--1.1.sql
--- b/contrib/dblink/dblink--1.1.sql
***************
*** 0 ****
--- 1,231 ----
+ /* contrib/dblink/dblink--1.1.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION dblink" to load this file. \quit
+ 
+ -- dblink_connect now restricts non-superusers to password
+ -- authenticated connections
+ CREATE FUNCTION dblink_connect (text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_connect'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_connect (text, text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_connect'
+ LANGUAGE C STRICT;
+ 
+ -- dblink_connect_u allows non-superusers to use
+ -- non-password authenticated connections, but initially
+ -- privileges are revoked from public
+ CREATE FUNCTION dblink_connect_u (text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_connect'
+ LANGUAGE C STRICT SECURITY DEFINER;
+ 
+ CREATE FUNCTION dblink_connect_u (text, text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_connect'
+ LANGUAGE C STRICT SECURITY DEFINER;
+ 
+ REVOKE ALL ON FUNCTION dblink_connect_u (text) FROM public;
+ REVOKE ALL ON FUNCTION dblink_connect_u (text, text) FROM public;
+ 
+ CREATE FUNCTION dblink_disconnect ()
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_disconnect'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_disconnect (text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_disconnect'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_open (text, text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_open'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_open (text, text, boolean)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_open'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_open (text, text, text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_open'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_open (text, text, text, boolean)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_open'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_fetch (text, int)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_fetch'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_fetch (text, int, boolean)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_fetch'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_fetch (text, text, int)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_fetch'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_fetch (text, text, int, boolean)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_fetch'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_close (text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_close'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_close (text, boolean)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_close'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_close (text, text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_close'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_close (text, text, boolean)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_close'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink (text, text)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_record'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink (text, text, boolean)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_record'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink (text)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_record'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink (text, boolean)
+ RETURNS setof record
+ AS 'MODULE_PATHNAME','dblink_record'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_exec (text, text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_exec'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_exec (text, text, boolean)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_exec'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_exec (text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_exec'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_exec (text,boolean)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_exec'
+ LANGUAGE C STRICT;
+ 
+ CREATE TYPE dblink_pkey_results AS (position int, colname text);
+ 
+ CREATE FUNCTION dblink_get_pkey (text)
+ RETURNS setof dblink_pkey_results
+ AS 'MODULE_PATHNAME','dblink_get_pkey'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_build_sql_insert (text, int2vector, int, _text, _text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_build_sql_insert'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_build_sql_delete (text, int2vector, int, _text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_build_sql_delete'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_build_sql_update (text, int2vector, int, _text, _text)
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_build_sql_update'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_current_query ()
+ RETURNS text
+ AS 'MODULE_PATHNAME','dblink_current_query'
+ LANGUAGE C;
+ 
+ CREATE FUNCTION dblink_send_query(text, text)
+ RETURNS int4
+ AS 'MODULE_PATHNAME', 'dblink_send_query'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_is_busy(text)
+ RETURNS int4
+ AS 'MODULE_PATHNAME', 'dblink_is_busy'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_get_result(text)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME', 'dblink_get_result'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_get_result(text, bool)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME', 'dblink_get_result'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_get_connections()
+ RETURNS text[]
+ AS 'MODULE_PATHNAME', 'dblink_get_connections'
+ LANGUAGE C;
+ 
+ CREATE FUNCTION dblink_cancel_query(text)
+ RETURNS text
+ AS 'MODULE_PATHNAME', 'dblink_cancel_query'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_error_message(text)
+ RETURNS text
+ AS 'MODULE_PATHNAME', 'dblink_error_message'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_get_notify(
+     OUT notify_name TEXT,
+     OUT be_pid INT4,
+     OUT extra TEXT
+ )
+ RETURNS setof record
+ AS 'MODULE_PATHNAME', 'dblink_get_notify'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_get_notify(
+     conname TEXT,
+     OUT notify_name TEXT,
+     OUT be_pid INT4,
+     OUT extra TEXT
+ )
+ RETURNS setof record
+ AS 'MODULE_PATHNAME', 'dblink_get_notify'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION dblink_fdw_validator(
+     options text[],
+     catalog oid
+ )
+ RETURNS boolean
+ AS 'MODULE_PATHNAME', 'dblink_fdw_validator'
+ LANGUAGE C STRICT;
diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 36a8e3e..1687c53 100644
*** a/contrib/dblink/dblink.c
--- b/contrib/dblink/dblink.c
***************
*** 36,43 ****
--- 36,46 ----
  
  #include "libpq-fe.h"
  #include "funcapi.h"
+ #include "access/reloptions.h"
  #include "catalog/indexing.h"
  #include "catalog/namespace.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_user_mapping.h"
  #include "catalog/pg_type.h"
  #include "executor/spi.h"
  #include "foreign/foreign.h"
*************** validate_pkattnums(Relation rel,
*** 2411,2413 ****
--- 2414,2516 ----
  					 errmsg("invalid attribute number %d", pkattnum)));
  	}
  }
+ 
+ 
+ /*
+  * Describes the valid options for postgresql FDW, server, and user mapping.
+  */
+ struct ConnectionOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which option may appear */
+ };
+ 
+ /*
+  * Copied from fe-connect.c PQconninfoOptions.
+  *
+  * The list is small - don't bother with bsearch if it stays so.
+  */
+ static struct ConnectionOption libpq_conninfo_options[] = {
+ 	{"authtype", ForeignServerRelationId},
+ 	{"service", ForeignServerRelationId},
+ 	{"user", UserMappingRelationId},
+ 	{"password", UserMappingRelationId},
+ 	{"connect_timeout", ForeignServerRelationId},
+ 	{"dbname", ForeignServerRelationId},
+ 	{"host", ForeignServerRelationId},
+ 	{"hostaddr", ForeignServerRelationId},
+ 	{"port", ForeignServerRelationId},
+ 	{"tty", ForeignServerRelationId},
+ 	{"options", ForeignServerRelationId},
+ 	{"requiressl", ForeignServerRelationId},
+ 	{"sslmode", ForeignServerRelationId},
+ 	{"gsslib", ForeignServerRelationId},
+ 	{NULL, InvalidOid}
+ };
+ 
+ 
+ /*
+  * Check if the provided option is one of libpq conninfo options.
+  * context is the Oid of the catalog the option came from, or 0 if we
+  * don't care.
+  */
+ static bool
+ is_conninfo_option(const char *option, Oid context)
+ {
+ 	struct ConnectionOption *opt;
+ 
+ 	for (opt = libpq_conninfo_options; opt->optname; opt++)
+ 		if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
+ 			return true;
+ 	return false;
+ }
+ 
+ 
+ /*
+  * Validate the generic option given to SERVER or USER MAPPING.
+  * Raise an ERROR if the option or its value is considered
+  * invalid.
+  *
+  * Valid server options are all libpq conninfo options except
+  * user and password -- these may only appear in USER MAPPING options.
+  */
+ PG_FUNCTION_INFO_V1(dblink_fdw_validator);
+ Datum
+ dblink_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 
+ 	ListCell   *cell;
+ 
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = lfirst(cell);
+ 
+ 		if (!is_conninfo_option(def->defname, catalog))
+ 		{
+ 			struct ConnectionOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = libpq_conninfo_options; opt->optname; opt++)
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_SYNTAX_ERROR),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 
+ 			PG_RETURN_BOOL(false);
+ 		}
+ 	}
+ 
+ 	PG_RETURN_BOOL(true);
+ }
diff --git a/contrib/dblink/dblink.control b/contrib/dblink/dblink.control
index 4333a9b..39f439a 100644
*** a/contrib/dblink/dblink.control
--- b/contrib/dblink/dblink.control
***************
*** 1,5 ****
  # dblink extension
  comment = 'connect to other PostgreSQL databases from within a database'
! default_version = '1.0'
  module_pathname = '$libdir/dblink'
  relocatable = true
--- 1,5 ----
  # dblink extension
  comment = 'connect to other PostgreSQL databases from within a database'
! default_version = '1.1'
  module_pathname = '$libdir/dblink'
  relocatable = true
diff --git a/contrib/dblink/dblink.h b/contrib/dblink/dblink.h
index 935d283..fd11658 100644
*** a/contrib/dblink/dblink.h
--- b/contrib/dblink/dblink.h
*************** extern Datum dblink_build_sql_delete(PG_
*** 58,62 ****
--- 58,63 ----
  extern Datum dblink_build_sql_update(PG_FUNCTION_ARGS);
  extern Datum dblink_current_query(PG_FUNCTION_ARGS);
  extern Datum dblink_get_notify(PG_FUNCTION_ARGS);
+ extern Datum dblink_fdw_validator(PG_FUNCTION_ARGS);
  
  #endif   /* DBLINK_H */
diff --git a/contrib/dblink/expected/dblink.out b/contrib/dblink/expected/dblink.out
index 511dd5e..0605354 100644
*** a/contrib/dblink/expected/dblink.out
--- b/contrib/dblink/expected/dblink.out
*************** SELECT dblink_disconnect('dtest1');
*** 785,792 ****
  
  -- test foreign data wrapper functionality
  CREATE USER dblink_regression_test;
! CREATE FOREIGN DATA WRAPPER postgresql;
! CREATE SERVER fdtest FOREIGN DATA WRAPPER postgresql OPTIONS (dbname 'contrib_regression');
  CREATE USER MAPPING FOR public SERVER fdtest;
  GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
  GRANT EXECUTE ON FUNCTION dblink_connect_u(text, text) TO dblink_regression_test;
--- 785,792 ----
  
  -- test foreign data wrapper functionality
  CREATE USER dblink_regression_test;
! CREATE FOREIGN DATA WRAPPER dblink_fdw VALIDATOR dblink_fdw_validator;
! CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw OPTIONS (dbname 'contrib_regression');
  CREATE USER MAPPING FOR public SERVER fdtest;
  GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
  GRANT EXECUTE ON FUNCTION dblink_connect_u(text, text) TO dblink_regression_test;
*************** REVOKE EXECUTE ON FUNCTION dblink_connec
*** 825,831 ****
  DROP USER dblink_regression_test;
  DROP USER MAPPING FOR public SERVER fdtest;
  DROP SERVER fdtest;
! DROP FOREIGN DATA WRAPPER postgresql;
  -- test asynchronous notifications
  SELECT dblink_connect('dbname=contrib_regression');
   dblink_connect 
--- 825,831 ----
  DROP USER dblink_regression_test;
  DROP USER MAPPING FOR public SERVER fdtest;
  DROP SERVER fdtest;
! DROP FOREIGN DATA WRAPPER dblink_fdw;
  -- test asynchronous notifications
  SELECT dblink_connect('dbname=contrib_regression');
   dblink_connect 
diff --git a/contrib/dblink/sql/dblink.sql b/contrib/dblink/sql/dblink.sql
index 8c8ffe2..288ebf8 100644
*** a/contrib/dblink/sql/dblink.sql
--- b/contrib/dblink/sql/dblink.sql
*************** SELECT dblink_disconnect('dtest1');
*** 361,368 ****
  -- test foreign data wrapper functionality
  CREATE USER dblink_regression_test;
  
! CREATE FOREIGN DATA WRAPPER postgresql;
! CREATE SERVER fdtest FOREIGN DATA WRAPPER postgresql OPTIONS (dbname 'contrib_regression');
  CREATE USER MAPPING FOR public SERVER fdtest;
  GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
  GRANT EXECUTE ON FUNCTION dblink_connect_u(text, text) TO dblink_regression_test;
--- 361,368 ----
  -- test foreign data wrapper functionality
  CREATE USER dblink_regression_test;
  
! CREATE FOREIGN DATA WRAPPER dblink_fdw VALIDATOR dblink_fdw_validator;
! CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw OPTIONS (dbname 'contrib_regression');
  CREATE USER MAPPING FOR public SERVER fdtest;
  GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
  GRANT EXECUTE ON FUNCTION dblink_connect_u(text, text) TO dblink_regression_test;
*************** REVOKE EXECUTE ON FUNCTION dblink_connec
*** 381,387 ****
  DROP USER dblink_regression_test;
  DROP USER MAPPING FOR public SERVER fdtest;
  DROP SERVER fdtest;
! DROP FOREIGN DATA WRAPPER postgresql;
  
  -- test asynchronous notifications
  SELECT dblink_connect('dbname=contrib_regression');
--- 381,387 ----
  DROP USER dblink_regression_test;
  DROP USER MAPPING FOR public SERVER fdtest;
  DROP SERVER fdtest;
! DROP FOREIGN DATA WRAPPER dblink_fdw;
  
  -- test asynchronous notifications
  SELECT dblink_connect('dbname=contrib_regression');
diff --git a/doc/src/sgml/dblink.sgml b/doc/src/sgml/dblink.sgml
index 855495c..613f447 100644
*** a/doc/src/sgml/dblink.sgml
--- b/doc/src/sgml/dblink.sgml
*************** dblink_connect(text connname, text conns
*** 47,55 ****
     <para>
      The connection string may also be the name of an existing foreign
      server.  It is recommended to use
!     the <function>postgresql_fdw_validator</function> when defining
!     the corresponding foreign-data wrapper.  See the example below, as
!     well as the following:
      <simplelist type="inline">
       <member><xref linkend="sql-createforeigndatawrapper"></member>
       <member><xref linkend="sql-createserver"></member>
--- 47,58 ----
     <para>
      The connection string may also be the name of an existing foreign
      server.  It is recommended to use
!     the <function>dblink_fdw_validator</function> when defining
!     the corresponding foreign-data wrapper.
!     This validator function was added in <productname>PostgreSQL</> 9.2, and
!     it has been called <function>postgresql_fdw_validator</function> in older
!     versions.
!     See the example below, as well as the following:
      <simplelist type="inline">
       <member><xref linkend="sql-createforeigndatawrapper"></member>
       <member><xref linkend="sql-createserver"></member>
*************** SELECT dblink_connect('myconn', 'dbname=
*** 136,143 ****
  --       DETAIL:  Non-superuser cannot connect if the server does not request a password.
  --       HINT:  Target server's authentication method must be changed.
  CREATE USER dblink_regression_test WITH PASSWORD 'secret';
! CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;
! CREATE SERVER fdtest FOREIGN DATA WRAPPER postgresql OPTIONS (hostaddr '127.0.0.1', dbname 'contrib_regression');
  
  CREATE USER MAPPING FOR dblink_regression_test SERVER fdtest OPTIONS (user 'dblink_regression_test', password 'secret');
  GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
--- 139,146 ----
  --       DETAIL:  Non-superuser cannot connect if the server does not request a password.
  --       HINT:  Target server's authentication method must be changed.
  CREATE USER dblink_regression_test WITH PASSWORD 'secret';
! CREATE FOREIGN DATA WRAPPER dblink_fdw VALIDATOR dblink_fdw_validator;
! CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw OPTIONS (hostaddr '127.0.0.1', dbname 'contrib_regression');
  
  CREATE USER MAPPING FOR dblink_regression_test SERVER fdtest OPTIONS (user 'dblink_regression_test', password 'secret');
  GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
*************** REVOKE SELECT ON TABLE foo FROM  dblink_
*** 173,179 ****
  DROP USER MAPPING FOR dblink_regression_test SERVER fdtest;
  DROP USER dblink_regression_test;
  DROP SERVER fdtest;
! DROP FOREIGN DATA WRAPPER postgresql;
  </screen>
    </refsect1>
   </refentry>
--- 176,182 ----
  DROP USER MAPPING FOR dblink_regression_test SERVER fdtest;
  DROP USER dblink_regression_test;
  DROP SERVER fdtest;
! DROP FOREIGN DATA WRAPPER dblink_fdw;
  </screen>
    </refsect1>
   </refentry>
diff --git a/doc/src/sgml/ref/create_foreign_data_wrapper.sgml b/doc/src/sgml/ref/create_foreign_data_wrapper.sgml
index 804fb47..0d346fd 100644
*** a/doc/src/sgml/ref/create_foreign_data_wrapper.sgml
--- b/doc/src/sgml/ref/create_foreign_data_wrapper.sgml
*************** CREATE FOREIGN DATA WRAPPER <replaceable
*** 123,133 ****
    </para>
  
    <para>
!    There is one built-in foreign-data wrapper validator function
!    provided:
!    <filename>postgresql_fdw_validator</filename>, which accepts
     options corresponding to <application>libpq</> connection
!    parameters.
    </para>
   </refsect1>
  
--- 123,134 ----
    </para>
  
    <para>
!    Until <productname>PostgreSQL</productname> 9.1, there was one built-in
!    foreign-data wrapper validator function provided:
!    <function>postgresql_fdw_validator</function>, which accepts
     options corresponding to <application>libpq</> connection
!    parameters.  But it has been moved to <filename>contrib/dblink</> with
!    renaming to <function>dblink_fdw_validator</function>.
    </para>
   </refsect1>
  
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index c4c2a61..6831c70 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
***************
*** 25,31 ****
  
  
  extern Datum pg_options_to_table(PG_FUNCTION_ARGS);
- extern Datum postgresql_fdw_validator(PG_FUNCTION_ARGS);
  
  
  
--- 25,30 ----
*************** pg_options_to_table(PG_FUNCTION_ARGS)
*** 401,504 ****
  
  
  /*
-  * Describes the valid options for postgresql FDW, server, and user mapping.
-  */
- struct ConnectionOption
- {
- 	const char *optname;
- 	Oid			optcontext;		/* Oid of catalog in which option may appear */
- };
- 
- /*
-  * Copied from fe-connect.c PQconninfoOptions.
-  *
-  * The list is small - don't bother with bsearch if it stays so.
-  */
- static struct ConnectionOption libpq_conninfo_options[] = {
- 	{"authtype", ForeignServerRelationId},
- 	{"service", ForeignServerRelationId},
- 	{"user", UserMappingRelationId},
- 	{"password", UserMappingRelationId},
- 	{"connect_timeout", ForeignServerRelationId},
- 	{"dbname", ForeignServerRelationId},
- 	{"host", ForeignServerRelationId},
- 	{"hostaddr", ForeignServerRelationId},
- 	{"port", ForeignServerRelationId},
- 	{"tty", ForeignServerRelationId},
- 	{"options", ForeignServerRelationId},
- 	{"requiressl", ForeignServerRelationId},
- 	{"sslmode", ForeignServerRelationId},
- 	{"gsslib", ForeignServerRelationId},
- 	{NULL, InvalidOid}
- };
- 
- 
- /*
-  * Check if the provided option is one of libpq conninfo options.
-  * context is the Oid of the catalog the option came from, or 0 if we
-  * don't care.
-  */
- static bool
- is_conninfo_option(const char *option, Oid context)
- {
- 	struct ConnectionOption *opt;
- 
- 	for (opt = libpq_conninfo_options; opt->optname; opt++)
- 		if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
- 			return true;
- 	return false;
- }
- 
- 
- /*
-  * Validate the generic option given to SERVER or USER MAPPING.
-  * Raise an ERROR if the option or its value is considered
-  * invalid.
-  *
-  * Valid server options are all libpq conninfo options except
-  * user and password -- these may only appear in USER MAPPING options.
-  */
- Datum
- postgresql_fdw_validator(PG_FUNCTION_ARGS)
- {
- 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
- 	Oid			catalog = PG_GETARG_OID(1);
- 
- 	ListCell   *cell;
- 
- 	foreach(cell, options_list)
- 	{
- 		DefElem    *def = lfirst(cell);
- 
- 		if (!is_conninfo_option(def->defname, catalog))
- 		{
- 			struct ConnectionOption *opt;
- 			StringInfoData buf;
- 
- 			/*
- 			 * Unknown option specified, complain about it. Provide a hint
- 			 * with list of valid options for the object.
- 			 */
- 			initStringInfo(&buf);
- 			for (opt = libpq_conninfo_options; opt->optname; opt++)
- 				if (catalog == opt->optcontext)
- 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
- 									 opt->optname);
- 
- 			ereport(ERROR,
- 					(errcode(ERRCODE_SYNTAX_ERROR),
- 					 errmsg("invalid option \"%s\"", def->defname),
- 					 errhint("Valid options in this context are: %s",
- 							 buf.data)));
- 
- 			PG_RETURN_BOOL(false);
- 		}
- 	}
- 
- 	PG_RETURN_BOOL(true);
- }
- 
- /*
   * get_foreign_data_wrapper_oid - given a FDW name, look up the OID
   *
   * If missing_ok is false, throw an error if name not found.  If true, just
--- 400,405 ----
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 8700d0d..8970998 100644
*** a/src/include/catalog/pg_proc.h
--- b/src/include/catalog/pg_proc.h
*************** DESCR("filenode identifier of relation")
*** 3399,3407 ****
  DATA(insert OID = 3034 ( pg_relation_filepath	PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 25 "2205" _null_ _null_ _null_ _null_ pg_relation_filepath _null_ _null_ _null_ ));
  DESCR("file path of relation");
  
- DATA(insert OID = 2316 ( postgresql_fdw_validator PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 16 "1009 26" _null_ _null_ _null_ _null_ postgresql_fdw_validator _null_ _null_ _null_));
- DESCR("(internal)");
- 
  DATA(insert OID = 2290 (  record_in			PGNSP PGUID 12 1 0 0 0 f f f f t f s 3 0 2249 "2275 26 23" _null_ _null_ _null_ _null_	record_in _null_ _null_ _null_ ));
  DESCR("I/O");
  DATA(insert OID = 2291 (  record_out		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 2275 "2249" _null_ _null_ _null_ _null_ record_out _null_ _null_ _null_ ));
--- 3399,3404 ----
diff --git a/src/test/regress/expected/foreign_data.out b/src/test/regress/expected/foreign_data.out
index ba86883..161fbe7 100644
*** a/src/test/regress/expected/foreign_data.out
--- b/src/test/regress/expected/foreign_data.out
*************** CREATE ROLE regress_test_role2;
*** 13,18 ****
--- 13,33 ----
  CREATE ROLE regress_test_role_super SUPERUSER;
  CREATE ROLE regress_test_indirect;
  CREATE ROLE unprivileged_role;
+ -- validator for this test
+ CREATE FUNCTION postgresql_fdw_validator(text[], oid) RETURNS boolean AS $$
+ DECLARE
+ BEGIN
+ 	IF $1::text LIKE '%foo%' THEN
+ 		RAISE 'invalid option "foo"'
+ 			USING HINT = 'Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, requiressl, sslmode, gsslib';
+ 	ELSIF $1::text LIKE '%username%' THEN
+ 		RAISE 'invalid option "username"'
+ 			USING HINT = 'Valid options in this context are: user, password';
+ 	END IF;
+ 
+ 	RETURN true;
+ END
+ $$ LANGUAGE plpgsql;
  CREATE FOREIGN DATA WRAPPER dummy;
  COMMENT ON FOREIGN DATA WRAPPER dummy IS 'useless';
  CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;
*************** DROP FOREIGN DATA WRAPPER postgresql CAS
*** 1201,1206 ****
--- 1216,1222 ----
  DROP FOREIGN DATA WRAPPER dummy CASCADE;
  NOTICE:  drop cascades to server s0
  \c
+ DROP FUNCTION postgresql_fdw_validator(text[], oid);
  DROP ROLE foreign_data_user;
  -- At this point we should have no wrappers, no servers, and no mappings.
  SELECT fdwname, fdwhandler, fdwvalidator, fdwoptions FROM pg_foreign_data_wrapper;
diff --git a/src/test/regress/sql/foreign_data.sql b/src/test/regress/sql/foreign_data.sql
index 0c95672..9cf9ca7 100644
*** a/src/test/regress/sql/foreign_data.sql
--- b/src/test/regress/sql/foreign_data.sql
*************** CREATE ROLE regress_test_role_super SUPE
*** 20,25 ****
--- 20,41 ----
  CREATE ROLE regress_test_indirect;
  CREATE ROLE unprivileged_role;
  
+ -- validator for this test
+ CREATE FUNCTION postgresql_fdw_validator(text[], oid) RETURNS boolean AS $$
+ DECLARE
+ BEGIN
+ 	IF $1::text LIKE '%foo%' THEN
+ 		RAISE 'invalid option "foo"'
+ 			USING HINT = 'Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, requiressl, sslmode, gsslib';
+ 	ELSIF $1::text LIKE '%username%' THEN
+ 		RAISE 'invalid option "username"'
+ 			USING HINT = 'Valid options in this context are: user, password';
+ 	END IF;
+ 
+ 	RETURN true;
+ END
+ $$ LANGUAGE plpgsql;
+ 
  CREATE FOREIGN DATA WRAPPER dummy;
  COMMENT ON FOREIGN DATA WRAPPER dummy IS 'useless';
  CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;
*************** DROP ROLE regress_test_role2;
*** 495,500 ****
--- 511,517 ----
  DROP FOREIGN DATA WRAPPER postgresql CASCADE;
  DROP FOREIGN DATA WRAPPER dummy CASCADE;
  \c
+ DROP FUNCTION postgresql_fdw_validator(text[], oid);
  DROP ROLE foreign_data_user;
  
  -- At this point we should have no wrappers, no servers, and no mappings.

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 46394a8..bb541e3 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 25,30 ****
--- 25,31 ----
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
  #include "utils/rel.h"
  #include "utils/syscache.h"
  
*************** PG_FUNCTION_INFO_V1(file_fdw_validator);
*** 93,99 ****
  /*
   * FDW callback routines
   */
! static FdwPlan *filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel);
  static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
--- 94,100 ----
  /*
   * FDW callback routines
   */
! static void filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel);
  static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
*************** get_file_fdw_attribute_options(Oid relid
*** 406,432 ****
  
  /*
   * filePlanForeignScan
!  *		Create a FdwPlan for a scan on the foreign table
   */
! static FdwPlan *
  filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel)
  {
! 	FdwPlan    *fdwplan;
  	char	   *filename;
  	List	   *options;
  
  	/* Fetch options --- we only need filename at this point */
  	fileGetOptions(foreigntableid, &filename, &options);
  
! 	/* Construct FdwPlan with cost estimates */
! 	fdwplan = makeNode(FdwPlan);
  	estimate_costs(root, baserel, filename,
! 				   &fdwplan->startup_cost, &fdwplan->total_cost);
! 	fdwplan->fdw_private = NIL; /* not used */
  
! 	return fdwplan;
  }
  
  /*
--- 407,443 ----
  
  /*
   * filePlanForeignScan
!  *		Create possible access paths for a scan on the foreign table
!  *
!  *		Currently we don't support any push-down feature, so there is only one
!  *		possible access path, which simply returns all records in the order in
!  *		the data file.
   */
! static void
  filePlanForeignScan(Oid foreigntableid,
  					PlannerInfo *root,
  					RelOptInfo *baserel)
  {
! 	ForeignPath *pathnode = makeNode(ForeignPath);
  	char	   *filename;
  	List	   *options;
  
  	/* Fetch options --- we only need filename at this point */
  	fileGetOptions(foreigntableid, &filename, &options);
  
! 	/* Create a ForeignPath node and add it as only one possible path. */
! 	pathnode = create_foreignscan_path(root, baserel);
! 	pathnode->fdw_private = NIL;
  	estimate_costs(root, baserel, filename,
! 				   &pathnode->path.startup_cost, &pathnode->path.total_cost);
! 	pathnode->path.rows = baserel->rows;
! 	add_path(baserel, (Path *) pathnode);
  
! 	/*
! 	 * If data file was sorted, and we knew it somehow, we can create another
! 	 * ForeignPath node with valid pathkeys to tell planner that sorting this
! 	 * file by such key is not expensive.
! 	 */
  }
  
  /*
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 76ff243..63fe8bd 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
***************
*** 88,108 ****
  
      <para>
  <programlisting>
! FdwPlan *
  PlanForeignScan (Oid foreigntableid,
                   PlannerInfo *root,
                   RelOptInfo *baserel);
  </programlisting>
  
!      Plan a scan on a foreign table. This is called when a query is planned.
       <literal>foreigntableid</> is the <structname>pg_class</> OID of the
       foreign table.  <literal>root</> is the planner's global information
       about the query, and <literal>baserel</> is the planner's information
       about this table.
!      The function must return a palloc'd struct that contains cost estimates
!      plus any FDW-private information that is needed to execute the foreign
!      scan at a later time.  (Note that the private information must be
!      represented in a form that <function>copyObject</> knows how to copy.)
      </para>
  
      <para>
--- 88,117 ----
  
      <para>
  <programlisting>
! void
  PlanForeignScan (Oid foreigntableid,
                   PlannerInfo *root,
                   RelOptInfo *baserel);
  </programlisting>
  
!      Create possible access paths for a scan on a foreign table. This is
!      called when a query is planned.
       <literal>foreigntableid</> is the <structname>pg_class</> OID of the
       foreign table.  <literal>root</> is the planner's global information
       about the query, and <literal>baserel</> is the planner's information
       about this table.
!     </para>
! 
!     <para>
!      The function must generate at least one access path for a scan on the
!      foreign table and call <function>add_path</> to add it to
!      <literal>baserel-&gt;pathlist</>.  The function may generate extra
!      access paths, e.g. a path which has valid <literal>pathkeys</> for sorted
!      result.  Each access path should contain cost estimates, and can contain
!      any FDW-private information that is needed to execute the foreign scan at
!      a later time.
!      (Note that the private information must be represented in a form that
!      <function>copyObject</> knows how to copy.)
      </para>
  
      <para>
*************** BeginForeignScan (ForeignScanState *node
*** 159,167 ****
       its <structfield>fdw_state</> field is still NULL.  Information about
       the table to scan is accessible through the
       <structname>ForeignScanState</> node (in particular, from the underlying
!      <structname>ForeignScan</> plan node, which contains a pointer to the
!      <structname>FdwPlan</> structure returned by
!      <function>PlanForeignScan</>).
      </para>
  
      <para>
--- 168,175 ----
       its <structfield>fdw_state</> field is still NULL.  Information about
       the table to scan is accessible through the
       <structname>ForeignScanState</> node (in particular, from the underlying
!      <structname>ForeignScan</> plan node, which contains FDW-private
!      information about it provided by <function>PlanForeignScan</>).
      </para>
  
      <para>
*************** EndForeignScan (ForeignScanState *node);
*** 228,236 ****
      </para>
  
      <para>
!      The <structname>FdwRoutine</> and <structname>FdwPlan</> struct types
!      are declared in <filename>src/include/foreign/fdwapi.h</>, which see
!      for additional details.
      </para>
  
     </sect1>
--- 236,244 ----
      </para>
  
      <para>
!      The <structname>FdwRoutine</> struct type is declared
!      in <filename>src/include/foreign/fdwapi.h</>, which see for additional
!      details.
      </para>
  
     </sect1>
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 7fec4db..9b2f688 100644
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
*************** _copyForeignScan(const ForeignScan *from
*** 591,611 ****
  	 * copy remainder of node
  	 */
  	COPY_SCALAR_FIELD(fsSystemCol);
- 	COPY_NODE_FIELD(fdwplan);
- 
- 	return newnode;
- }
- 
- /*
-  * _copyFdwPlan
-  */
- static FdwPlan *
- _copyFdwPlan(const FdwPlan *from)
- {
- 	FdwPlan    *newnode = makeNode(FdwPlan);
- 
- 	COPY_SCALAR_FIELD(startup_cost);
- 	COPY_SCALAR_FIELD(total_cost);
  	COPY_NODE_FIELD(fdw_private);
  
  	return newnode;
--- 591,596 ----
*************** copyObject(const void *from)
*** 3842,3850 ****
  		case T_ForeignScan:
  			retval = _copyForeignScan(from);
  			break;
- 		case T_FdwPlan:
- 			retval = _copyFdwPlan(from);
- 			break;
  		case T_Join:
  			retval = _copyJoin(from);
  			break;
--- 3827,3832 ----
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 25a215e..08b74fb 100644
*** a/src/backend/nodes/outfuncs.c
--- b/src/backend/nodes/outfuncs.c
*************** _outForeignScan(StringInfo str, const Fo
*** 558,573 ****
  	_outScanInfo(str, (const Scan *) node);
  
  	WRITE_BOOL_FIELD(fsSystemCol);
- 	WRITE_NODE_FIELD(fdwplan);
- }
- 
- static void
- _outFdwPlan(StringInfo str, const FdwPlan *node)
- {
- 	WRITE_NODE_TYPE("FDWPLAN");
- 
- 	WRITE_FLOAT_FIELD(startup_cost, "%.2f");
- 	WRITE_FLOAT_FIELD(total_cost, "%.2f");
  	WRITE_NODE_FIELD(fdw_private);
  }
  
--- 558,563 ----
*************** _outForeignPath(StringInfo str, const Fo
*** 1572,1578 ****
  
  	_outPathInfo(str, (const Path *) node);
  
! 	WRITE_NODE_FIELD(fdwplan);
  }
  
  static void
--- 1562,1568 ----
  
  	_outPathInfo(str, (const Path *) node);
  
! 	WRITE_NODE_FIELD(fdw_private);
  }
  
  static void
*************** _outNode(StringInfo str, const void *obj
*** 2745,2753 ****
  			case T_ForeignScan:
  				_outForeignScan(str, obj);
  				break;
- 			case T_FdwPlan:
- 				_outFdwPlan(str, obj);
- 				break;
  			case T_Join:
  				_outJoin(str, obj);
  				break;
--- 2735,2740 ----
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 8f03417..060d49d 100644
*** a/src/backend/optimizer/path/allpaths.c
--- b/src/backend/optimizer/path/allpaths.c
***************
*** 18,23 ****
--- 18,24 ----
  #include <math.h>
  
  #include "catalog/pg_class.h"
+ #include "foreign/fdwapi.h"
  #include "nodes/nodeFuncs.h"
  #ifdef OPTIMIZER_DEBUG
  #include "nodes/print.h"
*************** set_foreign_size(PlannerInfo *root, RelO
*** 399,411 ****
  
  /*
   * set_foreign_pathlist
!  *		Build the (single) access path for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
! 	/* Generate appropriate path */
! 	add_path(rel, (Path *) create_foreignscan_path(root, rel));
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
--- 400,414 ----
  
  /*
   * set_foreign_pathlist
!  *		Build access paths for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
! 	FdwRoutine	   *fdwroutine;
! 
! 	fdwroutine = GetFdwRoutineByRelId(rte->relid);
! 	fdwroutine->PlanForeignScan(rte->relid, root, rel);
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 9ac0c99..c348fd6 100644
*** a/src/backend/optimizer/plan/createplan.c
--- b/src/backend/optimizer/plan/createplan.c
*************** static CteScan *make_ctescan(List *qptli
*** 121,127 ****
  static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
  				   Index scanrelid, int wtParam);
  static ForeignScan *make_foreignscan(List *qptlist, List *qpqual,
! 				 Index scanrelid, bool fsSystemCol, FdwPlan *fdwplan);
  static BitmapAnd *make_bitmap_and(List *bitmapplans);
  static BitmapOr *make_bitmap_or(List *bitmapplans);
  static NestLoop *make_nestloop(List *tlist,
--- 121,127 ----
  static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
  				   Index scanrelid, int wtParam);
  static ForeignScan *make_foreignscan(List *qptlist, List *qpqual,
! 				 Index scanrelid, bool fsSystemCol, List *fdw_private);
  static BitmapAnd *make_bitmap_and(List *bitmapplans);
  static BitmapOr *make_bitmap_or(List *bitmapplans);
  static NestLoop *make_nestloop(List *tlist,
*************** create_foreignscan_plan(PlannerInfo *roo
*** 1847,1853 ****
  								 scan_clauses,
  								 scan_relid,
  								 fsSystemCol,
! 								 best_path->fdwplan);
  
  	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
  
--- 1847,1853 ----
  								 scan_clauses,
  								 scan_relid,
  								 fsSystemCol,
! 								 best_path->fdw_private);
  
  	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
  
*************** make_foreignscan(List *qptlist,
*** 3189,3195 ****
  				 List *qpqual,
  				 Index scanrelid,
  				 bool fsSystemCol,
! 				 FdwPlan *fdwplan)
  {
  	ForeignScan *node = makeNode(ForeignScan);
  	Plan	   *plan = &node->scan.plan;
--- 3189,3195 ----
  				 List *qpqual,
  				 Index scanrelid,
  				 bool fsSystemCol,
! 				 List *fdw_private)
  {
  	ForeignScan *node = makeNode(ForeignScan);
  	Plan	   *plan = &node->scan.plan;
*************** make_foreignscan(List *qptlist,
*** 3201,3207 ****
  	plan->righttree = NULL;
  	node->scan.scanrelid = scanrelid;
  	node->fsSystemCol = fsSystemCol;
! 	node->fdwplan = fdwplan;
  
  	return node;
  }
--- 3201,3207 ----
  	plan->righttree = NULL;
  	node->scan.scanrelid = scanrelid;
  	node->fsSystemCol = fsSystemCol;
! 	node->fdw_private = fdw_private;
  
  	return node;
  }
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index d29b454..9c285a9 100644
*** a/src/backend/optimizer/util/pathnode.c
--- b/src/backend/optimizer/util/pathnode.c
*************** create_worktablescan_path(PlannerInfo *r
*** 1764,1801 ****
  
  /*
   * create_foreignscan_path
!  *	  Creates a path corresponding to a scan of a foreign table,
!  *	  returning the pathnode.
   */
  ForeignPath *
  create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel)
  {
  	ForeignPath *pathnode = makeNode(ForeignPath);
- 	RangeTblEntry *rte;
- 	FdwRoutine *fdwroutine;
- 	FdwPlan    *fdwplan;
  
  	pathnode->path.pathtype = T_ForeignScan;
  	pathnode->path.parent = rel;
! 	pathnode->path.pathkeys = NIL;		/* result is always unordered */
  	pathnode->path.required_outer = NULL;
  	pathnode->path.param_clauses = NIL;
  
! 	/* Get FDW's callback info */
! 	rte = planner_rt_fetch(rel->relid, root);
! 	fdwroutine = GetFdwRoutineByRelId(rte->relid);
! 
! 	/* Let the FDW do its planning */
! 	fdwplan = fdwroutine->PlanForeignScan(rte->relid, root, rel);
! 	if (fdwplan == NULL || !IsA(fdwplan, FdwPlan))
! 		elog(ERROR, "foreign-data wrapper PlanForeignScan function for relation %u did not return an FdwPlan struct",
! 			 rte->relid);
! 	pathnode->fdwplan = fdwplan;
! 
! 	/* use costs estimated by FDW */
! 	pathnode->path.rows = rel->rows;
! 	pathnode->path.startup_cost = fdwplan->startup_cost;
! 	pathnode->path.total_cost = fdwplan->total_cost;
  
  	return pathnode;
  }
--- 1764,1795 ----
  
  /*
   * create_foreignscan_path
!  *	  Creates a path corresponding to a scan of a foreign table, and returns
!  *	  the pathnode.
!  *
!  *	  It's assumed that this function is called from PlanForeignScan
!  *	  imeplementation of FDWs, but not from planner directly; planner never
!  *	  calls this function directly.  Generated ForeignPath node has valid
!  *	  values for only requried fields, so each FDW should set optional fields
!  *	  as they want.
!  *
!  *	  If FDW needs to pass FDW-specific information from planner to executor,
!  *	  fdw_private field is available.  Its type is List *, so you can store
!  *	  Node subclass objects.  Planner will copy fdw_private of cheapest
!  *	  ForeignPath to ForeignScan plan node.
   */
  ForeignPath *
  create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel)
  {
  	ForeignPath *pathnode = makeNode(ForeignPath);
  
  	pathnode->path.pathtype = T_ForeignScan;
  	pathnode->path.parent = rel;
! 	pathnode->path.pathkeys = NIL;
  	pathnode->path.required_outer = NULL;
  	pathnode->path.param_clauses = NIL;
  
! 	pathnode->fdw_private = NIL;
  
  	return pathnode;
  }
diff --git a/src/include/foreign/fdwapi.h b/src/include/foreign/fdwapi.h
index 3696623..4831e7c 100644
*** a/src/include/foreign/fdwapi.h
--- b/src/include/foreign/fdwapi.h
*************** struct ExplainState;
*** 20,58 ****
  
  
  /*
-  * FdwPlan is the information returned to the planner by PlanForeignScan.
-  */
- typedef struct FdwPlan
- {
- 	NodeTag		type;
- 
- 	/*
- 	 * Cost estimation info. The startup_cost is time before retrieving the
- 	 * first row, so it should include costs of connecting to the remote host,
- 	 * sending over the query, etc.  Note that PlanForeignScan also ought to
- 	 * set baserel->rows and baserel->width if it can produce any usable
- 	 * estimates of those values.
- 	 */
- 	Cost		startup_cost;	/* cost expended before fetching any tuples */
- 	Cost		total_cost;		/* total cost (assuming all tuples fetched) */
- 
- 	/*
- 	 * FDW private data, which will be available at execution time.
- 	 *
- 	 * Note that everything in this list must be copiable by copyObject(). One
- 	 * way to store an arbitrary blob of bytes is to represent it as a bytea
- 	 * Const.  Usually, though, you'll be better off choosing a representation
- 	 * that can be dumped usefully by nodeToString().
- 	 */
- 	List	   *fdw_private;
- } FdwPlan;
- 
- 
- /*
   * Callback function signatures --- see fdwhandler.sgml for more info.
   */
  
! typedef FdwPlan *(*PlanForeignScan_function) (Oid foreigntableid,
  														  PlannerInfo *root,
  														RelOptInfo *baserel);
  
--- 20,29 ----
  
  
  /*
   * Callback function signatures --- see fdwhandler.sgml for more info.
   */
  
! typedef void (*PlanForeignScan_function) (Oid foreigntableid,
  														  PlannerInfo *root,
  														RelOptInfo *baserel);
  
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 0e7d184..905458f 100644
*** a/src/include/nodes/nodes.h
--- b/src/include/nodes/nodes.h
*************** typedef enum NodeTag
*** 62,68 ****
  	T_CteScan,
  	T_WorkTableScan,
  	T_ForeignScan,
- 	T_FdwPlan,
  	T_Join,
  	T_NestLoop,
  	T_MergeJoin,
--- 62,67 ----
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 7d90b91..23d9256 100644
*** a/src/include/nodes/plannodes.h
--- b/src/include/nodes/plannodes.h
*************** typedef struct ForeignScan
*** 468,475 ****
  {
  	Scan		scan;
  	bool		fsSystemCol;	/* true if any "system column" is needed */
! 	/* use struct pointer to avoid including fdwapi.h here */
! 	struct FdwPlan *fdwplan;
  } ForeignScan;
  
  
--- 468,474 ----
  {
  	Scan		scan;
  	bool		fsSystemCol;	/* true if any "system column" is needed */
! 	List	   *fdw_private;
  } ForeignScan;
  
  
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 6ba920a..1acc4f8 100644
*** a/src/include/nodes/relation.h
--- b/src/include/nodes/relation.h
*************** typedef struct TidPath
*** 794,805 ****
  
  /*
   * ForeignPath represents a scan of a foreign table
   */
  typedef struct ForeignPath
  {
  	Path		path;
! 	/* use struct pointer to avoid including fdwapi.h here */
! 	struct FdwPlan *fdwplan;
  } ForeignPath;
  
  /*
--- 794,810 ----
  
  /*
   * ForeignPath represents a scan of a foreign table
+  *
+  * fdw_private is a list of FDW private data, which will be available at
+  * execution time.  Note that everything in this list must be copiable
+  * by copyObject().  One way to store an arbitrary blob of bytes is to
+  * represent it as a bytea Const.  Usually, though, you'll be better off
+  * choosing a representation that can be dumped usefully by nodeToString().
   */
  typedef struct ForeignPath
  {
  	Path		path;
! 	List	   *fdw_private;
  } ForeignPath;
  
  /*

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...4a4e30c .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,556 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 		case XACT_READ_COMMITTED:
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't need to clean up at end of subtransactions, because they might
+ 	 * be recovered to consistent state with savepoints.
+ 	 */
+ 	if (!isTopLevel)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...7ca2767 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,210 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	nspname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "nspname");
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	relname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 								InvalidAttrNumber, "relname");
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 *
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					colname = GetFdwOptionValue(InvalidOid, InvalidOid, relid,
+ 												attr, "colname");
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...c1e2e82 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,592 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, requiressl, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = $1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_45 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+ (1 row)
+ 
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ SELECT srvname FROM pgsql_fdw_connections;
+  srvname 
+ ---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...13035c1 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,241 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ 	{"requiressl", ForeignServerRelationId, true},
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ 	{"gsslib", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(strVal(def->arg), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, strVal(def->arg))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = strVal(d->arg);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...8bf3fc0 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,859 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private information, such as remote SQL statements, which are
+  * stored in fdw_private list.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	List	   *fdw_private;	/* FDW-private information passed to executor */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static void pgsqlPlanForeignScan(Oid foreigntableid,
+ 								 PlannerInfo *root,
+ 								 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create possible scan paths for a scan on the foreign table
+  */
+ static void
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	const char	   *fetch_count_str;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/*
+ 	 * Generate remote query string, and estimate cost of this scan.
+ 	 */
+ 	sql = deparseSql(foreigntableid, root, baserel);
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &startup_cost, &total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/* Use specified fetch_count instead of default value, if any. */
+ 	fetch_count_str = GetFdwOptionValue(InvalidOid, InvalidOid, foreigntableid,
+ 										InvalidAttrNumber, "fetch_count");
+ 	if (fetch_count_str != NULL)
+ 		fetch_count = strtol(fetch_count_str, NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Create ForeignScan path node for this scan, and add it to baserel. */
+ 	add_path(baserel, (Path *)
+ 			 create_foreignscan_path(root, baserel,
+ 									 baserel->rows,
+ 									 startup_cost,
+ 									 total_cost,
+ 									 NIL,			/* no pathkeys */
+ 									 NULL,			/* no outer rel eigher */
+ 									 NIL,			/* no param clause */
+ 									 fdw_private));	/* store remote SQL */
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 
+ 	fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	List		   *fdw_private;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...f6394ce .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,28 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...b3fac96 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,248 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+ FETCH c;
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+ ERROR OUT;          -- ERROR
+ SELECT srvname FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...30fa7f5 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,261 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    If isolation level of local transaction is <literal>SERIALIZABLE</literal>,
+    <literal>SERIALIZABLE</literal> is used for remote transaction.  Otherwise,
+    if isolation level of local transaction is one of
+    <literal>READ UNCOMMITTED</literal>, <literal>READ COMMITTED</literal> or
+    <literal>REPEATABLE READ</literal>, then <literal>REPEATABLE READ</literal>
+    is used for remote transaction.
+    <literal>READ UNCOMMITTED</literal> and <literal>READ COMMITTED</literal>
+    are never used for remote transaction, because even
+    <literal>READ COMMITTED</literal> transaction might produce inconsistent
+    results, if remote data have been updated between two remote queries.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 64ba8ec..94b2ea9 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2181,2186 ****
--- 2181,2209 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 9fda7ad..4cf0489 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 650,655 ****
--- 650,656 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index 7ca2767..044f057 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 35,46 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
--- 35,53 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
! deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel, bool *has_param)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 51,56 ****
--- 58,64 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 59,73 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
  	if (baserel->baserestrictinfo != NIL)
  	{
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
--- 67,91 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
+ 	*has_param = false;
  	if (baserel->baserestrictinfo != NIL)
  	{
+ 		List	   *local_qual = NIL;
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 76,81 ****
--- 94,113 ----
  			List		   *attrs;
  
  			/*
+ 			 * Determine whether the qual can be pushed down or not.  If a qual
+ 			 * can be pushed down and it contains external param, tell that to
+ 			 * caller in order to fall back to fixed costs.
+ 			 */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 			{
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 				if (contain_ext_param((Node*) ri->clause))
+ 					*has_param = true;
+ 			}
+ 			else
+ 				local_qual = lappend(local_qual, ri);
+ 
+ 			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
  			 * SELECT clause of remote query.  We can ignore attributes
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 87,92 ****
--- 119,130 ----
  									PVC_RECURSE_PLACEHOLDERS);
  			attr_used = list_union(attr_used, attrs);
  		}
+ 
+ 		/*
+ 		 * Remove pushed down qualifiers from baserestrictinfo to avoid
+ 		 * redundant evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
  	}
  
  	/*
*************** deparseSql(Oid relid, PlannerInfo *root,
*** 204,210 ****
--- 242,473 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		/*
+ 		 * If function used by the expression is not built-in, it can't be
+ 		 * pushed down because it might has incompatible semantics on remote
+ 		 * side.
+ 		 */
+ 		case T_FuncExpr:
+ 			{
+ 				FuncExpr	   *fe = (FuncExpr *) node;
+ 				if (!is_builtin(fe->funcid))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index c1e2e82..51b347e 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 230,241 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 230,241 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: (((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 343,362 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- ===================================================================
  -- parameterized queries
--- 343,360 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
! (2 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
! (2 rows)
  
  -- ===================================================================
  -- parameterized queries
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 364,380 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 362,375 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (5 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 391,411 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 386,405 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c4) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st1(101, 101);
*** 422,442 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 416,435 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c5) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st3(20, 30);
*** 453,504 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = $1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_45 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- cleanup
  DEALLOCATE st1;
--- 446,491 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  -- cleanup
  DEALLOCATE st1;
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index 8bf3fc0..c12b0a7 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
*************** pgsqlPlanForeignScan(Oid foreigntableid,
*** 194,208 ****
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/*
  	 * Generate remote query string, and estimate cost of this scan.
  	 */
! 	sql = deparseSql(foreigntableid, root, baserel);
! 	table = GetForeignTable(foreigntableid);
! 	server = GetForeignServer(table->serverid);
! 	estimate_costs(root, baserel, sql, server->serverid,
! 				   &startup_cost, &total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
--- 194,225 ----
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
+ 	bool			has_param;
  
  	/*
  	 * Generate remote query string, and estimate cost of this scan.
+ 	 *
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL as part of push-down-able condition, we need to
+ 	 * groundless fixed costs because we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
  	 */
! 	sql = deparseSql(foreigntableid, root, baserel, &has_param);
! 	if (has_param)
! 	{
! 		startup_cost = CONNECTION_COSTS;
! 		total_cost = 10000;	/* groundless large costs */
! 	}
! 	else
! 	{
! 		table = GetForeignTable(foreigntableid);
! 		server = GetForeignServer(table->serverid);
! 		estimate_costs(root, baserel, sql, server->serverid,
! 					   &startup_cost, &total_cost);
! 	}
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index f6394ce..690d58b 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
*************** int ExtractConnectionOptions(List *defel
*** 23,28 ****
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid, PlannerInfo *root, RelOptInfo *baserel);
  
  #endif /* PGSQL_FDW_H */
--- 23,31 ----
  							 const char **values);
  
  /* in deparse.c */
! char *deparseSql(Oid relid,
! 				 PlannerInfo *root,
! 				 RelOptInfo *baserel,
! 				 bool *has_param);
  
  #endif /* PGSQL_FDW_H */
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index 30fa7f5..2375d8f 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 242,253 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
!    Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
! (3 rows)
  </synopsis>
   </sect2>
  
--- 242,252 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! ------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8861.66 rows=518 width=8)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
! (2 rows)
  </synopsis>
   </sect2>
  

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index c2faa62..0193aae 100644
*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 27,33 ****
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.h"
  #include "utils/rel.h"
! #include "utils/syscache.h"
  
  PG_MODULE_MAGIC;
  
--- 27,33 ----
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.h"
  #include "utils/rel.h"
! #include "utils/lsyscache.h"
  
  PG_MODULE_MAGIC;
  
*************** get_file_fdw_attribute_options(Oid relid
*** 346,399 ****
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		HeapTuple	tuple;
! 		Form_pg_attribute attr;
! 		Datum		datum;
! 		bool		isnull;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		/*
! 		 * We need the whole pg_attribute tuple not just what is in the
! 		 * tupleDesc, so must do a catalog lookup.
! 		 */
! 		tuple = SearchSysCache2(ATTNUM,
! 								RelationGetRelid(rel),
! 								Int16GetDatum(attnum));
! 		if (!HeapTupleIsValid(tuple))
! 			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
! 				 attnum, RelationGetRelid(rel));
! 		attr = (Form_pg_attribute) GETSTRUCT(tuple);
! 
! 		datum = SysCacheGetAttr(ATTNUM,
! 								tuple,
! 								Anum_pg_attribute_attfdwoptions,
! 								&isnull);
! 		if (!isnull)
  		{
! 			List	   *options = untransformRelOptions(datum);
! 			ListCell   *lc;
  
! 			foreach(lc, options)
  			{
! 				DefElem	   *def = (DefElem *) lfirst(lc);
! 
! 				if (strcmp(def->defname, "force_not_null") == 0)
  				{
! 					if (defGetBoolean(def))
! 					{
! 						char   *attname = pstrdup(NameStr(attr->attname));
  
! 						fnncolumns = lappend(fnncolumns, makeString(attname));
! 					}
  				}
- 				/* maybe in future handle other options here */
  			}
  		}
- 
- 		ReleaseSysCache(tuple);
  	}
  
  	heap_close(rel, AccessShareLock);
--- 346,374 ----
  	/* Retrieve FDW options for all user-defined attributes. */
  	for (attnum = 1; attnum <= natts; attnum++)
  	{
! 		List	   *options;
! 		ListCell   *lc;
  
  		/* Skip dropped attributes. */
  		if (tupleDesc->attrs[attnum - 1]->attisdropped)
  			continue;
  
! 		options = GetForeignColumnOptions(relid, attnum);
! 		foreach(lc, options)
  		{
! 			DefElem	   *def = (DefElem *) lfirst(lc);
  
! 			if (strcmp(def->defname, "force_not_null") == 0)
  			{
! 				if (defGetBoolean(def))
  				{
! 					char   *attname = pstrdup(get_attname(relid, attnum));
  
! 					fnncolumns = lappend(fnncolumns, makeString(attname));
  				}
  			}
+ 			/* maybe in future handle other options here */
  		}
  	}
  
  	heap_close(rel, AccessShareLock);
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 12c5f75..7900484 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** EndForeignScan (ForeignScanState *node);
*** 244,247 ****
--- 244,352 ----
  
     </sect1>
  
+    <sect1 id="fdw-helpers">
+     <title>Foreign Data Wrapper Helper Functions</title>
+ 
+     <para>
+      Several helper functions are exported from core so that authors of FDW
+      can get easy access to attributes of FDW-related objects such as FDW
+      options.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapper(Oid fdwid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given oid.  A
+      <structname>ForeignDataWrapper</structname> object contains oid of the
+      wrapper itself, oid of the owner of the wrapper, name of the wrapper, oid
+      of fdwhandler function, oid of fdwvalidator function, and FDW options in
+      the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServer(Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given oid.  A <structname>ForeignServer</structname>
+      object contains oid of the server, oid of the wrapper for the server, oid
+      of the owner of the server, name of the server, type of the server,
+      version of the server, and FDW options in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ UserMapping *
+ GetUserMapping(Oid userid, Oid serverid);
+ </programlisting>
+ 
+      This function returns a <structname>UserMapping</structname> object for a
+      user mapping with given oid pair.  A <structname>UserMapping</structname>
+      object contains oid of the user, oid of the server, and FDW options in the
+      form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignTable *
+ GetForeignTable(Oid relid);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignTable</structname> object for a
+      foreign table with given oid.  A <structname>ForeignTable</structname>
+      object contains oid of the foreign table, oid of the server for the table,
+      and FDW options in the form of list of <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+ <programlisting>
+ List *
+ GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
+ </programlisting>
+ 
+      This function returns per-column FDW options for a column with given
+      relation oid and attribute number in the form of list of
+      <structname>DefElem</structname>.
+     </para>
+ 
+     <para>
+      Some object types have name-based functions.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignDataWrapper *
+ GetForeignDataWrapperByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignDataWrapper</structname> object
+      for a foreign-data wrapper with given name.  If the wrapper is not found,
+      return NULL if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+ <programlisting>
+ ForeignServer *
+ GetForeignServerByName(const char *name, bool missing_ok);
+ </programlisting>
+ 
+      This function returns a <structname>ForeignServer</structname> object for
+      a foreign server with given name.  If the server is not found, return NULL
+      if missing_ok was true, otherwise raise an error.
+     </para>
+ 
+     <para>
+      To use any of these functions, you need to include
+      <filename>foreign/foreign.h</filename> in your source file.
+     </para>
+ 
+   </sect1>
+ 
   </chapter>
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index c4c2a61..4db26b5 100644
*** a/src/backend/foreign/foreign.c
--- b/src/backend/foreign/foreign.c
***************
*** 17,22 ****
--- 17,23 ----
  #include "catalog/pg_foreign_server.h"
  #include "catalog/pg_foreign_table.h"
  #include "catalog/pg_user_mapping.h"
+ #include "commands/defrem.h"
  #include "foreign/fdwapi.h"
  #include "foreign/foreign.h"
  #include "miscadmin.h"
*************** GetForeignTable(Oid relid)
*** 246,251 ****
--- 247,282 ----
  	return ft;
  }
  
+ /*
+  * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum as
+  * list of DefElem.
+  */
+ List *
+ GetForeignColumnOptions(Oid relid, AttrNumber attnum)
+ {
+ 	List	   *options;
+ 	HeapTuple	tp;
+ 	Datum		datum;
+ 	bool		isnull;
+ 
+ 	tp = SearchSysCache2(ATTNUM,
+ 						 ObjectIdGetDatum(relid),
+ 						 Int16GetDatum(attnum));
+ 	if (!HeapTupleIsValid(tp))
+ 		elog(ERROR, "cache lookup failed for attribute %d of relation %u", attnum, relid);
+ 	datum = SysCacheGetAttr(ATTNUM,
+ 							tp,
+ 							Anum_pg_attribute_attfdwoptions,
+ 							&isnull);
+ 	if (isnull)
+ 		options = NIL;
+ 	else
+ 		options = untransformRelOptions(datum);
+ 
+ 	ReleaseSysCache(tp);
+ 
+ 	return options;
+ }
  
  /*
   * GetFdwRoutine - call the specified foreign-data wrapper handler routine
diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h
index 191122d..4a4ce23 100644
*** a/src/include/foreign/foreign.h
--- b/src/include/foreign/foreign.h
*************** extern ForeignDataWrapper *GetForeignDat
*** 75,80 ****
--- 75,81 ----
  extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
  							bool missing_ok);
  extern ForeignTable *GetForeignTable(Oid relid);
+ extern List *GetForeignColumnOptions(Oid relid, AttrNumber attnum);
  
  extern Oid	get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok);
  extern Oid	get_foreign_server_oid(const char *servername, bool missing_ok);

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...4a4e30c .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,556 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 		case XACT_READ_COMMITTED:
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find appropriate
+ 	 * PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 			break;
+ 	}
+ 	if (entry != NULL)
+ 		hash_seq_term(&scan);
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * If the released connection was an orphan, just close it.
+ 	 */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't need to clean up at end of subtransactions, because they might
+ 	 * be recovered to consistent state with savepoints.
+ 	 */
+ 	if (!isTopLevel)
+ 		return;
+ 
+ 	/*
+ 	 * We don't care whether we are in TopTransaction or Subtransaction.
+ 	 * Anyway, we close the connection and reset the reference counter.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...de49211 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,233 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "commands/defrem.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid,
+ 		   PlannerInfo *root,
+ 		   RelOptInfo *baserel,
+ 		   ForeignTable *table)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	ListCell   *lc;
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	foreach(lc, table->options)
+ 	{
+ 		DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 		if (strcmp(def->defname, "nspname") == 0)
+ 			nspname = defGetString(def);
+ 		else if (strcmp(def->defname, "relname") == 0)
+ 			relname = defGetString(def);
+ 	}
+ 
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 *
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					List	   *options;
+ 					ListCell   *lc;
+ 
+ 					options = GetForeignColumnOptions(relid, attr);
+ 					foreach(lc, options)
+ 					{
+ 						DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 						if (strcmp(def->defname, "colname") == 0)
+ 						{
+ 							colname = defGetString(def);
+ 							break;
+ 						}
+ 					}
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...c1e2e82 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,592 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, requiressl, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = $1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_45 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+ (1 row)
+ 
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ SELECT srvname FROM pgsql_fdw_connections;
+  srvname 
+ ---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...a2a8927 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,242 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "commands/defrem.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ 	{"requiressl", ForeignServerRelationId, true},
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ 	{"gsslib", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(defGetString(def), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, defGetString(def))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = defGetString(d);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...d0d6767 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,880 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/defrem.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private information, such as remote SQL statements, which are
+  * stored in fdw_private list.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	List	   *fdw_private;	/* FDW-private information passed to executor */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static void pgsqlPlanForeignScan(Oid foreigntableid,
+ 								 PlannerInfo *root,
+ 								 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create possible scan paths for a scan on the foreign table
+  */
+ static void
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	ListCell	   *lc;
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	DefElem		   *def;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/*
+ 	 * Generate remote query string, and estimate cost of this scan.
+ 	 */
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	sql = deparseSql(foreigntableid, root, baserel, table);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &startup_cost, &total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/*
+ 	 * Use specified fetch_count instead of default value, if any.  If both
+ 	 * table and server have that option, use table's setting.
+ 	 */
+ 	def = NULL;
+ 	foreach(lc, table->options)
+ 	{
+ 		def = (DefElem *) lfirst(lc);
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 			break;
+  
+ 	}
+ 	if (lc != NULL)
+ 	{
+ 		foreach(lc, server->options)
+ 		{
+ 			def = (DefElem *) lfirst(lc);
+ 			if (strcmp(def->defname, "fetch_count") == 0)
+ 				break;
+ 	 
+ 		}
+ 	}
+ 	if (lc != NULL)
+ 		fetch_count = strtol(defGetString(def), NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Create ForeignScan path node for this scan, and add it to baserel. */
+ 	add_path(baserel, (Path *)
+ 			 create_foreignscan_path(root, baserel,
+ 									 baserel->rows,
+ 									 startup_cost,
+ 									 total_cost,
+ 									 NIL,			/* no pathkeys */
+ 									 NULL,			/* no outer rel eigher */
+ 									 NIL,			/* no param clause */
+ 									 fdw_private));	/* store remote SQL */
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 
+ 	fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	List		   *fdw_private;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...78a6abf .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,32 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "foreign/foreign.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid,
+ 				 PlannerInfo *root,
+ 				 RelOptInfo *baserel,
+ 				 ForeignTable *table);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...b3fac96 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,248 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+ FETCH c;
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+ ERROR OUT;          -- ERROR
+ SELECT srvname FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...30fa7f5 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,261 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    If isolation level of local transaction is <literal>SERIALIZABLE</literal>,
+    <literal>SERIALIZABLE</literal> is used for remote transaction.  Otherwise,
+    if isolation level of local transaction is one of
+    <literal>READ UNCOMMITTED</literal>, <literal>READ COMMITTED</literal> or
+    <literal>REPEATABLE READ</literal>, then <literal>REPEATABLE READ</literal>
+    is used for remote transaction.
+    <literal>READ UNCOMMITTED</literal> and <literal>READ COMMITTED</literal>
+    are never used for remote transaction, because even
+    <literal>READ COMMITTED</literal> transaction might produce inconsistent
+    results, if remote data have been updated between two remote queries.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 64ba8ec..94b2ea9 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2181,2186 ****
--- 2181,2209 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 9fda7ad..4cf0489 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 650,655 ****
--- 650,656 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index de49211..a023f44 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
*************** typedef struct foreign_executable_cxt
*** 36,50 ****
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.
   */
  char *
  deparseSql(Oid relid,
  		   PlannerInfo *root,
  		   RelOptInfo *baserel,
! 		   ForeignTable *table)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
--- 36,58 ----
  	RelOptInfo	   *foreignrel;
  } foreign_executable_cxt;
  
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
+ static bool contain_ext_param(Node *clause);
+ static bool contain_ext_param_walker(Node *node, void *context);
+ 
  /*
   * Deparse query representation into SQL statement which suits for remote
!  * PostgreSQL server.  Also some of quals in WHERE clause will be pushed down
!  * If they are safe to be evaluated on the remote side.
   */
  char *
  deparseSql(Oid relid,
  		   PlannerInfo *root,
  		   RelOptInfo *baserel,
! 		   ForeignTable *table,
! 		   bool *has_param)
  {
  	StringInfoData	foreign_relname;
  	StringInfoData	sql;			/* builder for SQL statement */
*************** deparseSql(Oid relid,
*** 56,61 ****
--- 64,70 ----
  	const char *relname = NULL;		/* plain relation name */
  	const char *q_nspname;			/* quoted namespace name */
  	const char *q_relname;			/* quoted relation name */
+ 	List	   *foreign_expr = NIL;	/* list of Expr* evaluated on remote */
  	int			i;
  	List	   *rtable = NIL;
  	List	   *context = NIL;
*************** deparseSql(Oid relid,
*** 64,78 ****
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which column should be retrieved for this scan.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
  	if (baserel->baserestrictinfo != NIL)
  	{
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
--- 73,97 ----
  	initStringInfo(&foreign_relname);
  
  	/*
! 	 * First of all, determine which qual can be pushed down.
! 	 *
! 	 * The expressions which satisfy is_foreign_expr() are deparsed into WHERE
! 	 * clause of result SQL string, and they could be removed from PlanState
! 	 * to avoid duplicate evaluation at ExecScan().
! 	 *
! 	 * We never change the quals in the Plan node, because this execution might
! 	 * be for a PREPAREd statement, thus the quals in the Plan node might be
! 	 * reused to construct another PlanState for subsequent EXECUTE statement.
  	 *
  	 * We do this before deparsing SELECT clause because attributes which are
  	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
  	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
  	 * clause to reduce overhead of tuple handling tuple and data transfer.
  	 */
+ 	*has_param = false;
  	if (baserel->baserestrictinfo != NIL)
  	{
+ 		List	   *local_qual = NIL;
  		ListCell   *lc;
  
  		foreach (lc, baserel->baserestrictinfo)
*************** deparseSql(Oid relid,
*** 81,86 ****
--- 100,119 ----
  			List		   *attrs;
  
  			/*
+ 			 * Determine whether the qual can be pushed down or not.  If a qual
+ 			 * can be pushed down and it contains external param, tell that to
+ 			 * caller in order to fall back to fixed costs.
+ 			 */
+ 			if (is_foreign_expr(root, baserel, ri->clause))
+ 			{
+ 				foreign_expr = lappend(foreign_expr, ri->clause);
+ 				if (contain_ext_param((Node*) ri->clause))
+ 					*has_param = true;
+ 			}
+ 			else
+ 				local_qual = lappend(local_qual, ri);
+ 
+ 			/*
  			 * We need to know which attributes are used in qual evaluated
  			 * on the local server, because they should be listed in the
  			 * SELECT clause of remote query.  We can ignore attributes
*************** deparseSql(Oid relid,
*** 92,97 ****
--- 125,136 ----
  									PVC_RECURSE_PLACEHOLDERS);
  			attr_used = list_union(attr_used, attrs);
  		}
+ 
+ 		/*
+ 		 * Remove pushed down qualifiers from baserestrictinfo to avoid
+ 		 * redundant evaluation.
+ 		 */
+ 		baserel->baserestrictinfo = local_qual;
  	}
  
  	/*
*************** deparseSql(Oid relid,
*** 227,233 ****
--- 266,497 ----
  	 */
  	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
  
+ 	/*
+ 	 * deparse WHERE clause
+ 	 */
+ 	if (foreign_expr != NIL)
+ 	{
+ 		Node	   *node;
+ 
+ 		node = (Node *) make_ands_explicit(foreign_expr);
+ 		appendStringInfo(&sql, " WHERE %s ",
+ 			deparse_expression(node, context, false, false));
+ 		list_free(foreign_expr);
+ 		foreign_expr = NIL;
+ 	}
+ 
  	elog(DEBUG3, "Remote SQL: %s", sql.data);
  	return sql.data;
  }
  
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		/*
+ 		 * If function used by the expression is not built-in, it can't be
+ 		 * pushed down because it might has incompatible semantics on remote
+ 		 * side.
+ 		 */
+ 		case T_FuncExpr:
+ 			{
+ 				FuncExpr	   *fe = (FuncExpr *) node;
+ 				if (!is_builtin(fe->funcid))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
+ /*
+  * contain_ext_param
+  *	  Recursively search for Param nodes within a clause.
+  *
+  *	  Returns true if any parameter reference node with relkind PARAM_EXTERN
+  *	  found.
+  *
+  * This does not descend into subqueries, and so should be used only after
+  * reduction of sublinks to subplans, or in contexts where it's known there
+  * are no subqueries.  There mustn't be outer-aggregate references either.
+  *
+  * XXX: These functions could be in core, src/backend/optimizer/util/clauses.c.
+  */
+ static bool
+ contain_ext_param(Node *clause)
+ {
+ 	return contain_ext_param_walker(clause, NULL);
+ }
+ 
+ static bool
+ contain_ext_param_walker(Node *node, void *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 	if (IsA(node, Param))
+ 	{
+ 		Param	   *param = (Param *) node;
+ 
+ 		if (param->paramkind == PARAM_EXTERN)
+ 			return true;		/* abort the tree traversal and return true */
+ 	}
+ 	return expression_tree_walker(node, contain_ext_param_walker, context);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index c1e2e82..51b347e 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 230,241 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 230,241 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: (((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 101) 
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 343,362 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = abs(c2))
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- ===================================================================
  -- parameterized queries
--- 343,360 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                                  QUERY PLAN                                                                 
! --------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = abs(c2)) 
! (2 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = c2) 
! (2 rows)
  
  -- ===================================================================
  -- parameterized queries
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 364,380 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 362,375 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                      
! ------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 1) 
!    ->  Foreign Scan on ft2 t2
!          Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" = 2) 
! (5 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 391,411 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 386,405 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c4) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st1(101, 101);
*** 422,442 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
! (12 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 416,435 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                               QUERY PLAN                                                                               
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" < 20) 
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
!                            Filter: (date_part('dow'::text, c5) = 6::double precision)
!                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE ("C 1" > 10) 
! (11 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st3(20, 30);
*** 453,504 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = $1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_45 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- cleanup
  DEALLOCATE st1;
--- 446,491 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: DECLARE pgsql_fdw_cursor_46 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ("C 1" = 1) 
! (2 rows)
  
  -- cleanup
  DEALLOCATE st1;
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index d0d6767..7c39307 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
*************** pgsqlPlanForeignScan(Oid foreigntableid,
*** 196,210 ****
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/*
  	 * Generate remote query string, and estimate cost of this scan.
  	 */
  	table = GetForeignTable(foreigntableid);
! 	server = GetForeignServer(table->serverid);
! 	sql = deparseSql(foreigntableid, root, baserel, table);
! 	estimate_costs(root, baserel, sql, server->serverid,
! 				   &startup_cost, &total_cost);
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
--- 196,227 ----
  	List		   *fdw_private = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
+ 	bool			has_param;
  
  	/*
  	 * Generate remote query string, and estimate cost of this scan.
+ 	 *
+ 	 * If the baserestrictinfo contains any Param node with paramkind
+ 	 * PARAM_EXTERNAL as part of push-down-able condition, we need to
+ 	 * groundless fixed costs because we can't get actual parameter values
+ 	 * here, so we use fixed and large costs as second best so that planner
+ 	 * tend to choose custom plan.
+ 	 *
+ 	 * See comments in plancache.c for details of custom plan.
  	 */
  	table = GetForeignTable(foreigntableid);
! 	sql = deparseSql(foreigntableid, root, baserel, table, &has_param);
! 	if (has_param)
! 	{
! 		startup_cost = CONNECTION_COSTS;
! 		total_cost = 10000;	/* groundless large costs */
! 	}
! 	else
! 	{
! 		server = GetForeignServer(table->serverid);
! 		estimate_costs(root, baserel, sql, server->serverid,
! 					   &startup_cost, &total_cost);
! 	}
  
  	/*
  	 * Store plain SELECT statement in private area of FdwPlan.  This will be
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index 78a6abf..020d282 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
*************** int ExtractConnectionOptions(List *defel
*** 27,32 ****
  char *deparseSql(Oid relid,
  				 PlannerInfo *root,
  				 RelOptInfo *baserel,
! 				 ForeignTable *table);
  
  #endif /* PGSQL_FDW_H */
--- 27,33 ----
  char *deparseSql(Oid relid,
  				 PlannerInfo *root,
  				 RelOptInfo *baserel,
! 				 ForeignTable *table,
! 				 bool *has_param);
  
  #endif /* PGSQL_FDW_H */
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index 30fa7f5..2375d8f 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 242,253 ****
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                         QUERY PLAN
! --------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
!    Filter: (abalance < 0)
!    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
! (3 rows)
  </synopsis>
   </sect2>
  
--- 242,252 ----
    </para>
  <synopsis>
  postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
!                                                                    QUERY PLAN
! ------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on pgbench_accounts  (cost=100.00..8861.66 rows=518 width=8)
!    Remote SQL: DECLARE pgsql_fdw_cursor_1 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts WHERE (abalance < 0)
! (2 rows)
  </synopsis>
   </sect2>
  

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...c971bd7 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,555 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 		case XACT_READ_COMMITTED:
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 		{
+ 			hash_seq_term(&scan);
+ 			break;
+ 		}
+ 	}
+ 
+ 	/* If the released connection was an orphan, just close it. */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't need to clean up at end of subtransactions, because they might
+ 	 * be recovered to consistent state with savepoints.
+ 	 */
+ 	if (!isTopLevel)
+ 		return;
+ 
+ 	/*
+ 	 * Here, it must be after abort of top level transaction.  Disconnect and
+ 	 * forget every referrer.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...de49211 .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,233 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "commands/defrem.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.
+  */
+ char *
+ deparseSql(Oid relid,
+ 		   PlannerInfo *root,
+ 		   RelOptInfo *baserel,
+ 		   ForeignTable *table)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 	ListCell   *lc;
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 	int			i;
+ 	List	   *rtable = NIL;
+ 	List	   *context = NIL;
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * Determine foreign relation's qualified name.  This is necessary for
+ 	 * FROM clause and SELECT clause.
+ 	 */
+ 	foreach(lc, table->options)
+ 	{
+ 		DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 		if (strcmp(def->defname, "nspname") == 0)
+ 			nspname = defGetString(def);
+ 		else if (strcmp(def->defname, "relname") == 0)
+ 			relname = defGetString(def);
+ 	}
+ 
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	q_nspname = quote_identifier(nspname);
+ 
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	appendStringInfo(&foreign_relname, "%s.%s", q_nspname, q_relname);
+ 
+ 	/*
+ 	 * We need to replace aliasname and colnames of the target relation so that
+ 	 * constructed remote query is valid.
+ 	 *
+ 	 * Note that we skip first empty element of simple_rel_array.  See also
+ 	 * comments of simple_rel_array and simple_rte_array for the rationale.
+ 	 */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		RangeTblEntry  *rte = copyObject(root->simple_rte_array[i]);
+ 		List		   *newcolnames = NIL;
+ 
+ 		if (i == baserel->relid)
+ 		{
+ 			/*
+ 			 * Create new list of column names which is used to deparse remote
+ 			 * query from specified names or local column names.  This list is
+ 			 * used by deparse_expression.
+ 			 */
+ 			for (attr = 1; attr <= baserel->max_attr; attr++)
+ 			{
+ 				char	   *colname = NULL;
+ 
+ 				/*
+ 				 * Get colname option for each undropped attribute.  If colname
+ 				 * option is not supplied, use local column name in remote
+ 				 * query.
+ 				 */
+ 				if (get_rte_attribute_is_dropped(rte, attr))
+ 					colname = "";
+ 				else
+ 				{
+ 					List	   *options;
+ 					ListCell   *lc;
+ 
+ 					options = GetForeignColumnOptions(relid, attr);
+ 					foreach(lc, options)
+ 					{
+ 						DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 						if (strcmp(def->defname, "colname") == 0)
+ 						{
+ 							colname = defGetString(def);
+ 							break;
+ 						}
+ 					}
+ 					if (colname == NULL)
+ 						colname = strVal(list_nth(rte->eref->colnames,
+ 												  attr - 1));
+ 				}
+ 				newcolnames = lappend(newcolnames, makeString(colname));
+ 			}
+ 			rte->alias = makeAlias(relname, newcolnames);
+ 		}
+ 		rtable = lappend(rtable, rte);
+ 	}
+ 	context = deparse_context_for_rtelist(rtable);
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			appendStringInfo(&sql, "%s",
+ 				deparse_expression((Node *) var, context, false, false));
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM %s", foreign_relname.data);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...c1e2e82 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,592 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, requiressl, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_22 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_23 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_28 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_29 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_34 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_35 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = $1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_45 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+ (1 row)
+ 
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ SELECT srvname FROM pgsql_fdw_connections;
+  srvname 
+ ---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...a2a8927 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,242 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "commands/defrem.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ 	{"requiressl", ForeignServerRelationId, true},
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ 	{"gsslib", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(defGetString(def), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, defGetString(def))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = defGetString(d);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...7ac37f8 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,879 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/defrem.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private information, such as remote SQL statements, which are
+  * stored in fdw_private list.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	List	   *fdw_private;	/* FDW-private information passed to executor */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static void pgsqlPlanForeignScan(Oid foreigntableid,
+ 								 PlannerInfo *root,
+ 								 RelOptInfo *baserel);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void estimate_costs(PlannerInfo *root,
+ 						   RelOptInfo *baserel,
+ 						   const char *sql,
+ 						   Oid serverid,
+ 						   Cost *startup_cost,
+ 						   Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlPlanForeignScan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlPlanForeignScan
+  *		Create possible scan paths for a scan on the foreign table
+  */
+ static void
+ pgsqlPlanForeignScan(Oid foreigntableid,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	ListCell	   *lc;
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	DefElem		   *def;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	List		   *fdw_private = NIL;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/*
+ 	 * Generate remote query string, and estimate cost of this scan.
+ 	 */
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	sql = deparseSql(foreigntableid, root, baserel, table);
+ 	estimate_costs(root, baserel, sql, server->serverid,
+ 				   &startup_cost, &total_cost);
+ 
+ 	/*
+ 	 * Store plain SELECT statement in private area of FdwPlan.  This will be
+ 	 * used for executing remote query and explaining scan.
+ 	 */
+ 	fdw_private = list_make1(makeString(sql));
+ 
+ 	/*
+ 	 * Use specified fetch_count instead of default value, if any.  Foreign
+ 	 * table option overrides server option.
+ 	 */
+ 	foreach(lc, table->options)
+ 	{
+ 		def = (DefElem *) lfirst(lc);
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 			break;
+  
+ 	}
+ 	if (lc == NULL)
+ 	{
+ 		foreach(lc, server->options)
+ 		{
+ 			def = (DefElem *) lfirst(lc);
+ 			if (strcmp(def->defname, "fetch_count") == 0)
+ 				break;
+ 	 
+ 		}
+ 	}
+ 	if (lc != NULL)
+ 		fetch_count = strtol(defGetString(def), NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Create ForeignScan path node for this scan, and add it to baserel. */
+ 	add_path(baserel, (Path *)
+ 			 create_foreignscan_path(root, baserel,
+ 									 baserel->rows,
+ 									 startup_cost,
+ 									 total_cost,
+ 									 NIL,			/* no pathkeys */
+ 									 NULL,			/* no outer rel eigher */
+ 									 NIL,			/* no param clause */
+ 									 fdw_private));	/* store remote SQL */
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 
+ 	fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of scanning a foreign table.
+  */
+ static void
+ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ 			   const char *sql, Oid serverid,
+ 			   Cost *startup_cost, Cost *total_cost)
+ {
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn = NULL;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	server = GetForeignServer(serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, false);
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, &baserel->rows, &baserel->width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 		ReleaseConnection(conn);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * baserel->width * baserel->tuples;
+ 	*total_cost += cpu_tuple_cost * baserel->tuples;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	List		   *fdw_private;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...78a6abf .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,32 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "foreign/foreign.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSql(Oid relid,
+ 				 PlannerInfo *root,
+ 				 RelOptInfo *baserel,
+ 				 ForeignTable *table);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...b3fac96 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,248 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+ FETCH c;
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+ ERROR OUT;          -- ERROR
+ SELECT srvname FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...30fa7f5 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,261 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    If isolation level of local transaction is <literal>SERIALIZABLE</literal>,
+    <literal>SERIALIZABLE</literal> is used for remote transaction.  Otherwise,
+    if isolation level of local transaction is one of
+    <literal>READ UNCOMMITTED</literal>, <literal>READ COMMITTED</literal> or
+    <literal>REPEATABLE READ</literal>, then <literal>REPEATABLE READ</literal>
+    is used for remote transaction.
+    <literal>READ UNCOMMITTED</literal> and <literal>READ COMMITTED</literal>
+    are never used for remote transaction, because even
+    <literal>READ COMMITTED</literal> transaction might produce inconsistent
+    results, if remote data have been updated between two remote queries.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 64ba8ec..94b2ea9 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2181,2186 ****
--- 2181,2209 ----
  	return list_make1(dpns);
  }
  
+ /* ----------
+  * deparse_context_for_rtelist	- Build deparse context for a list of RTEs
+  *
+  * Given the list of RangeTableEnetry, build deparsing context for an
+  * expression referencing those relations.	This is sufficient for uses of
+  * deparse_expression before plan has been created.
+  * ----------
+  */
+ List *
+ deparse_context_for_rtelist(List *rtable)
+ {
+ 	deparse_namespace *dpns;
+ 
+ 	dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
+ 
+ 	/* Build a minimal RTE for the rel */
+ 	dpns->rtable = rtable;
+ 	dpns->ctes = NIL;
+ 
+ 	/* Return a one-deep namespace stack */
+ 	return list_make1(dpns);
+ }
+ 
  /*
   * deparse_context_for_planstate	- Build deparse context for a plan
   *
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 9fda7ad..4cf0489 100644
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
*************** extern char *deparse_expression(Node *ex
*** 650,655 ****
--- 650,656 ----
  extern List *deparse_context_for(const char *aliasname, Oid relid);
  extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
  							  List *rtable);
+ extern List *deparse_context_for_rtelist(List *rtable);
  extern const char *quote_identifier(const char *ident);
  extern char *quote_qualified_identifier(const char *qualifier,
  						   const char *ident);

*** a/contrib/file_fdw/file_fdw.c
--- b/contrib/file_fdw/file_fdw.c
***************
*** 74,87 **** static const struct FileFdwOption valid_options[] = {
  };
  
  /*
!  * FDW-specific information for RelOptInfo.fdw_private.
   */
  typedef struct FileFdwPlanState
  {
  	char	   *filename;		/* file to read */
  	List	   *options;		/* merged COPY options, excluding filename */
- 	BlockNumber pages;			/* estimate of file's physical size */
- 	double		ntuples;		/* estimate of number of rows in file */
  } FileFdwPlanState;
  
  /*
--- 74,85 ----
  };
  
  /*
!  * FDW-specific information for RelOptInfo.fdw_state.
   */
  typedef struct FileFdwPlanState
  {
  	char	   *filename;		/* file to read */
  	List	   *options;		/* merged COPY options, excluding filename */
  } FileFdwPlanState;
  
  /*
***************
*** 132,140 **** static void fileGetOptions(Oid foreigntableid,
  			   char **filename, List **other_options);
  static List *get_file_fdw_attribute_options(Oid relid);
  static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
! 			  FileFdwPlanState *fdw_private);
  static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
- 			   FileFdwPlanState *fdw_private,
  			   Cost *startup_cost, Cost *total_cost);
  
  
--- 130,137 ----
  			   char **filename, List **other_options);
  static List *get_file_fdw_attribute_options(Oid relid);
  static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
! 			  FileFdwPlanState *fpstate);
  static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
  			   Cost *startup_cost, Cost *total_cost);
  
  
***************
*** 415,433 **** fileGetForeignRelSize(PlannerInfo *root,
  					  RelOptInfo *baserel,
  					  Oid foreigntableid)
  {
! 	FileFdwPlanState *fdw_private;
  
  	/*
  	 * Fetch options.  We only need filename at this point, but we might
  	 * as well get everything and not need to re-fetch it later in planning.
  	 */
! 	fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
! 	fileGetOptions(foreigntableid,
! 				   &fdw_private->filename, &fdw_private->options);
! 	baserel->fdw_private = (void *) fdw_private;
  
  	/* Estimate relation size */
! 	estimate_size(root, baserel, fdw_private);
  }
  
  /*
--- 412,429 ----
  					  RelOptInfo *baserel,
  					  Oid foreigntableid)
  {
! 	FileFdwPlanState *fpstate;
  
  	/*
  	 * Fetch options.  We only need filename at this point, but we might
  	 * as well get everything and not need to re-fetch it later in planning.
  	 */
! 	fpstate = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
! 	fileGetOptions(foreigntableid, &fpstate->filename, &fpstate->options);
! 	baserel->fdw_state = (void *) fpstate;
  
  	/* Estimate relation size */
! 	estimate_size(root, baserel, fpstate);
  }
  
  /*
***************
*** 443,455 **** fileGetForeignPaths(PlannerInfo *root,
  					RelOptInfo *baserel,
  					Oid foreigntableid)
  {
- 	FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
  	Cost		startup_cost;
  	Cost		total_cost;
  
  	/* Estimate costs */
! 	estimate_costs(root, baserel, fdw_private,
! 				   &startup_cost, &total_cost);
  
  	/* Create a ForeignPath node and add it as only possible path */
  	add_path(baserel, (Path *)
--- 439,449 ----
  					RelOptInfo *baserel,
  					Oid foreigntableid)
  {
  	Cost		startup_cost;
  	Cost		total_cost;
  
  	/* Estimate costs */
! 	estimate_costs(root, baserel, &startup_cost, &total_cost);
  
  	/* Create a ForeignPath node and add it as only possible path */
  	add_path(baserel, (Path *)
***************
*** 647,659 **** fileReScanForeignScan(ForeignScanState *node)
  /*
   * Estimate size of a foreign table.
   *
!  * The main result is returned in baserel->rows.  We also set
!  * fdw_private->pages and fdw_private->ntuples for later use in the cost
!  * calculation.
   */
  static void
  estimate_size(PlannerInfo *root, RelOptInfo *baserel,
! 			  FileFdwPlanState *fdw_private)
  {
  	struct stat stat_buf;
  	BlockNumber pages;
--- 641,652 ----
  /*
   * Estimate size of a foreign table.
   *
!  * The main result is returned in baserel->rows.  We also set baserel->pages
!  * and baserel->tuples for later use in the cost calculation.
   */
  static void
  estimate_size(PlannerInfo *root, RelOptInfo *baserel,
! 			  FileFdwPlanState *fpstate)
  {
  	struct stat stat_buf;
  	BlockNumber pages;
***************
*** 665,671 **** estimate_size(PlannerInfo *root, RelOptInfo *baserel,
  	 * Get size of the file.  It might not be there at plan time, though, in
  	 * which case we have to use a default estimate.
  	 */
! 	if (stat(fdw_private->filename, &stat_buf) < 0)
  		stat_buf.st_size = 10 * BLCKSZ;
  
  	/*
--- 658,664 ----
  	 * Get size of the file.  It might not be there at plan time, though, in
  	 * which case we have to use a default estimate.
  	 */
! 	if (stat(fpstate->filename, &stat_buf) < 0)
  		stat_buf.st_size = 10 * BLCKSZ;
  
  	/*
***************
*** 675,681 **** estimate_size(PlannerInfo *root, RelOptInfo *baserel,
  	if (pages < 1)
  		pages = 1;
  
! 	fdw_private->pages = pages;
  
  	/*
  	 * Estimate the number of tuples in the file.  We back into this estimate
--- 668,674 ----
  	if (pages < 1)
  		pages = 1;
  
! 	baserel->pages = pages;
  
  	/*
  	 * Estimate the number of tuples in the file.  We back into this estimate
***************
*** 688,694 **** estimate_size(PlannerInfo *root, RelOptInfo *baserel,
  
  	ntuples = clamp_row_est((double) stat_buf.st_size / (double) tuple_width);
  
! 	fdw_private->ntuples = ntuples;
  
  	/*
  	 * Now estimate the number of rows returned by the scan after applying the
--- 681,687 ----
  
  	ntuples = clamp_row_est((double) stat_buf.st_size / (double) tuple_width);
  
! 	baserel->tuples = ntuples;
  
  	/*
  	 * Now estimate the number of rows returned by the scan after applying the
***************
*** 715,725 **** estimate_size(PlannerInfo *root, RelOptInfo *baserel,
   */
  static void
  estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
- 			   FileFdwPlanState *fdw_private,
  			   Cost *startup_cost, Cost *total_cost)
  {
! 	BlockNumber pages = fdw_private->pages;
! 	double		ntuples = fdw_private->ntuples;
  	Cost		run_cost = 0;
  	Cost		cpu_per_tuple;
  
--- 708,717 ----
   */
  static void
  estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
  			   Cost *startup_cost, Cost *total_cost)
  {
! 	BlockNumber pages = baserel->pages;
! 	double		ntuples = baserel->tuples;
  	Cost		run_cost = 0;
  	Cost		cpu_per_tuple;
  
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
***************
*** 126,132 **** GetForeignRelSize (PlannerInfo *root,
      </para>
  
      <para>
!      <literal>baserel-&gt;fdw_private</> is a <type>void</> pointer that is
       available for use by FDW planning functions.  It can be used to pass
       information forward from <function>GetForeignRelSize</> to
       <function>GetForeignPaths</> and/or <function>GetForeignPaths</> to
--- 126,132 ----
      </para>
  
      <para>
!      <literal>baserel-&gt;fdw_state</> is a <type>void</> pointer that is
       available for use by FDW planning functions.  It can be used to pass
       information forward from <function>GetForeignRelSize</> to
       <function>GetForeignPaths</> and/or <function>GetForeignPaths</> to
*** a/src/backend/optimizer/util/relnode.c
--- b/src/backend/optimizer/util/relnode.c
***************
*** 114,120 **** build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
  	rel->subplan = NULL;
  	rel->subroot = NULL;
  	rel->fdwroutine = NULL;
! 	rel->fdw_private = NULL;
  	rel->baserestrictinfo = NIL;
  	rel->baserestrictcost.startup = 0;
  	rel->baserestrictcost.per_tuple = 0;
--- 114,120 ----
  	rel->subplan = NULL;
  	rel->subroot = NULL;
  	rel->fdwroutine = NULL;
! 	rel->fdw_state = NULL;
  	rel->baserestrictinfo = NIL;
  	rel->baserestrictcost.startup = 0;
  	rel->baserestrictcost.per_tuple = 0;
***************
*** 369,375 **** build_join_rel(PlannerInfo *root,
  	joinrel->subplan = NULL;
  	joinrel->subroot = NULL;
  	joinrel->fdwroutine = NULL;
! 	joinrel->fdw_private = NULL;
  	joinrel->baserestrictinfo = NIL;
  	joinrel->baserestrictcost.startup = 0;
  	joinrel->baserestrictcost.per_tuple = 0;
--- 369,375 ----
  	joinrel->subplan = NULL;
  	joinrel->subroot = NULL;
  	joinrel->fdwroutine = NULL;
! 	joinrel->fdw_state = NULL;
  	joinrel->baserestrictinfo = NIL;
  	joinrel->baserestrictcost.startup = 0;
  	joinrel->baserestrictcost.per_tuple = 0;
*** a/src/include/nodes/relation.h
--- b/src/include/nodes/relation.h
***************
*** 422,428 **** typedef struct RelOptInfo
  	PlannerInfo *subroot;		/* if subquery */
  	/* use "struct FdwRoutine" to avoid including fdwapi.h here */
  	struct FdwRoutine *fdwroutine;	/* if foreign table */
! 	void	   *fdw_private;	/* if foreign table */
  
  	/* used by various scans and joins: */
  	List	   *baserestrictinfo;		/* RestrictInfo structures (if base
--- 422,428 ----
  	PlannerInfo *subroot;		/* if subquery */
  	/* use "struct FdwRoutine" to avoid including fdwapi.h here */
  	struct FdwRoutine *fdwroutine;	/* if foreign table */
! 	void	   *fdw_state;		/* if foreign table */
  
  	/* used by various scans and joins: */
  	List	   *baserestrictinfo;		/* RestrictInfo structures (if base

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...c971bd7 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,555 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 		case XACT_READ_COMMITTED:
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 		{
+ 			hash_seq_term(&scan);
+ 			break;
+ 		}
+ 	}
+ 
+ 	/* If the released connection was an orphan, just close it. */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't need to clean up at end of subtransactions, because they might
+ 	 * be recovered to consistent state with savepoints.
+ 	 */
+ 	if (!isTopLevel)
+ 		return;
+ 
+ 	/*
+ 	 * Here, it must be after abort of top level transaction.  Disconnect and
+ 	 * forget every referrer.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...beb62fe .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,290 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "catalog/pg_class.h"
+ #include "commands/defrem.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Get string representation which can be used in SQL statement from a node.
+  */
+ static void deparseRelation(StringInfo buf, Oid relid, PlannerInfo *root,
+ 							bool need_prefix);
+ static void deparseVar(StringInfo buf, Var *node, PlannerInfo *root,
+ 					   RelOptInfo *baserel, bool need_prefix);
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.  This function just creates simple query string which
+  * consists of only SELECT and FROM clause.
+  */
+ char *
+ deparseSimpleSql(Oid relid,
+ 			     PlannerInfo *root,
+ 			     RelOptInfo *baserel,
+ 			     ForeignTable *table)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			deparseVar(&sql, var, root, baserel, false);
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM ");
+ 	deparseRelation(&sql, table->relid, root, true);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
+ /*
+  * Deparse node into buf, with relation qualifier if need_prefix was true.  If
+  * node is a column of a foreign table, use value of colname FDW option (if any)
+  * instead of attribute name.
+  */
+ static void
+ deparseVar(StringInfo buf,
+ 		   Var *node,
+ 		   PlannerInfo *root,
+ 		   RelOptInfo *baserel,
+ 		   bool need_prefix)
+ {
+ 	RangeTblEntry  *rte;
+ 	char		   *colname = NULL;
+ 	const char	   *q_colname = NULL;
+ 	List		   *options;
+ 	ListCell	   *lc;
+ 
+ 	/* node must not be any of OUTER_VAR,INNER_VAR and INDEX_VAR. */
+ 	Assert(node->varno >= 1 && node->varno <= root->simple_rel_array_size);
+ 
+ 	/* Get RangeTblEntry from array in PlannerInfo. */
+ 	rte = root->simple_rte_array[node->varno];
+ 
+ 	/*
+ 	 * If the node is a column of a foreign table, and it has colname FDW
+ 	 * option, use its value.
+ 	 */
+ 	if (rte->relkind == RELKIND_FOREIGN_TABLE)
+ 	{
+ 		options = GetForeignColumnOptions(rte->relid, node->varattno);
+ 		foreach(lc, options)
+ 		{
+ 			DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 			if (strcmp(def->defname, "colname") == 0)
+ 			{
+ 				colname = defGetString(def);
+ 				break;
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * If the node refers a column of a regular table or it doesn't have colname
+ 	 * FDW option, use attribute name.
+ 	 */
+ 	if (colname == NULL)
+ 		colname = get_attname(rte->relid, node->varattno);
+ 
+ 	if (need_prefix)
+ 	{
+ 		char *aliasname;
+ 		const char *q_aliasname;
+ 
+ 		if (rte->eref != NULL && rte->eref->aliasname != NULL)
+ 			aliasname = rte->eref->aliasname;
+ 		else if (rte->alias != NULL && rte->alias->aliasname != NULL)
+ 			aliasname = rte->alias->aliasname;
+ 
+ 		q_aliasname = quote_identifier(aliasname);
+ 		appendStringInfo(buf, "%s.", q_aliasname);
+ 	}
+ 
+ 	q_colname = quote_identifier(colname);
+ 	appendStringInfo(buf, "%s", q_colname);
+ }
+ 
+ /*
+  * Deparse table which has relid as oid into buf, with schema qualifier if
+  * need_prefix was true.  If relid points a foreign table, use value of relname
+  * FDW option (if any) instead of relation's name.  Similarly, nspname FDW
+  * option overrides schema name.
+  */
+ static void
+ deparseRelation(StringInfo buf,
+ 				Oid relid,
+ 				PlannerInfo *root,
+ 				bool need_prefix)
+ {
+ 	int			i;
+ 	RangeTblEntry *rte = NULL;
+ 	ListCell   *lc;
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 
+ 	/* Find RangeTblEntry for the relation from PlannerInfo. */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		if (root->simple_rte_array[i]->relid == relid)
+ 		{
+ 			rte = root->simple_rte_array[i];
+ 			break;
+ 		}
+ 	}
+ 	if (rte == NULL)
+ 		elog(ERROR, "relation with OID %u is not used in the query", relid);
+ 
+ 	/* If target is a foreign table, obtain additional catalog information. */
+ 	if (rte->relkind == RELKIND_FOREIGN_TABLE)
+ 	{
+ 		ForeignTable *table = GetForeignTable(rte->relid);
+ 
+ 		/*
+ 		 * Use value of FDW options if any, instead of the name of object
+ 		 * itself.
+ 		 */
+ 		foreach(lc, table->options)
+ 		{
+ 			DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 			if (need_prefix && strcmp(def->defname, "nspname") == 0)
+ 				nspname = defGetString(def);
+ 			else if (strcmp(def->defname, "relname") == 0)
+ 				relname = defGetString(def);
+ 		}
+ 	}
+ 
+ 	/* Quote each identifier, if necessary. */
+ 	if (need_prefix)
+ 	{
+ 		if (nspname == NULL)
+ 			nspname = get_namespace_name(get_rel_namespace(relid));
+ 		q_nspname = quote_identifier(nspname);
+ 	}
+ 
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	/* Construct relation reference into the buffer. */
+ 	if (need_prefix)
+ 		appendStringInfo(buf, "%s.", q_nspname);
+ 	appendStringInfo(buf, "%s", q_relname);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...5bac241 .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,592 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, requiressl, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_16 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_17 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: DECLARE pgsql_fdw_cursor_18 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                                                QUERY PLAN                                                                
+ -----------------------------------------------------------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Materialize
+          ->  Foreign Scan on ft2 t2
+                Filter: (c1 = 2)
+                Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (8 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_26 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_27 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                                                     QUERY PLAN                                                                     
+ ---------------------------------------------------------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: DECLARE pgsql_fdw_cursor_32 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  HashAggregate
+                      ->  Foreign Scan on ft2 t2
+                            Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                            Remote SQL: DECLARE pgsql_fdw_cursor_33 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (12 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_38 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_39 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                                                     QUERY PLAN                                                     
+ -------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = $1)
+    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+ (1 row)
+ 
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ SELECT srvname FROM pgsql_fdw_connections;
+  srvname 
+ ---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...a2a8927 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,242 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "commands/defrem.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ 	{"requiressl", ForeignServerRelationId, true},
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ 	{"gsslib", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(defGetString(def), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, defGetString(def))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = defGetString(d);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...370d240 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,1014 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/defrem.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "optimizer/planmain.h"
+ #include "optimizer/restrictinfo.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * FDW-specific information for RelOptInfo.fdw_private.  This is used to pass
+  * information from pgsqlGetForeignRelSize to pgsqlGetForeignPaths.
+  */
+ typedef struct PgsqlFdwPlanState {
+ 	/*
+ 	 * These are generated in GetForeignRelSize, and also used in subsequent
+ 	 * GetForeignPaths.
+ 	 * XXX If we can have enough statistics of remote data, we can defer 
+ 	 * estimating cost to GetForeignPaths, so then these would be unnecessary.
+ 	 */
+ 	char		   *sql;
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ } PgsqlFdwPlanState;
+ 
+ /*
+  * Index of FDW-private information, such as remote SQL statements, which are
+  * stored in fdw_private list.
+  */
+ enum FdwPrivateIndex {
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	List	   *fdw_private;	/* FDW-private information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static void pgsqlGetForeignRelSize(PlannerInfo *root,
+ 								   RelOptInfo *baserel,
+ 								   Oid foreigntableid);
+ static void pgsqlGetForeignPaths(PlannerInfo *root,
+ 								 RelOptInfo *baserel,
+ 								 Oid foreigntableid);
+ static ForeignScan *pgsqlGetForeignPlan(PlannerInfo *root,
+ 										RelOptInfo *baserel,
+ 										Oid foreigntableid,
+ 										ForeignPath *best_path,
+ 										List *tlist,
+ 										List *scan_clauses);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void get_remote_estimate(const char *sql,
+ 								PGconn *conn,
+ 								double *rows,
+ 								int *width,
+ 								Cost *startup_cost,
+ 								Cost *total_cost);
+ static void adjust_costs(double rows, int width,
+ 						 Cost *startup_cost, Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlGetForeignRelSize,
+ 	pgsqlGetForeignPaths,
+ 	pgsqlGetForeignPlan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlGetForeignRelSize
+  *		Estimate # of rows and width of the result of the scan
+  *
+  * If we have had enough statistics about foreign data, we can get good
+  * estimate of rows and width of this scan by calling
+  * set_baserel_size_estimates(), therefore we can avoid executing expensive
+  * EXPLAIN on remote side.  To achieve this, we need ANALYZE support for
+  * foreign tables by backend, and FDW-specific implementation of updating
+  * statistics.  But we don't have them at this moment, so estimate # of result
+  * rows on the basis of remote estimate for unconditional query and selectivity
+  * of the clauses.
+  */
+ static void
+ pgsqlGetForeignRelSize(PlannerInfo *root,
+ 					   RelOptInfo *baserel,
+ 					   Oid foreigntableid)
+ {
+ 	char		   *sql;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn;
+ 	double			rows;
+ 	int				width;
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ 	PgsqlFdwPlanState *planstate;
+ 
+ 	/* Retrieve catalog objects which are necessary to estimate rows. */
+ 	table = GetForeignTable(foreigntableid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 
+ 	/*
+ 	 * Create plain SELECT statement with no WHERE clause for this scan to
+ 	 * obtain meaningful rows estimation by executing EXPLAIN on remote server.
+ 	 */
+ 	sql = deparseSimpleSql(foreigntableid, root, baserel, table);
+ 	conn = GetConnection(server, user, false);
+ 	get_remote_estimate(sql, conn, &rows, &width, &startup_cost, &total_cost);
+ 	ReleaseConnection(conn);
+ 
+ 	/*
+ 	 * Estimate # of rows by calling set_baserel_size_estimates() with setting
+ 	 * baserel->tuples to the rows estimation of remote EXPLAIN.  We override
+ 	 * width estimation because set_baserel_size_estimates estimates it on the
+ 	 * basis of statistics which we don't actually have.
+ 	 */
+ 	baserel->tuples = rows;
+ 	set_baserel_size_estimates(root, baserel);
+ 	baserel->width = width;
+ 
+ 	/*
+ 	 * Pack obtained information into a object and store it in FDW-private area
+ 	 * of RelOptInfo to pass them to subsequent functions.
+ 	 */
+ 	planstate = palloc(sizeof(PgsqlFdwExecutionState));
+ 	planstate->sql = sql;
+ 	planstate->startup_cost = startup_cost;
+ 	planstate->total_cost = total_cost;
+ 	baserel->fdw_private = (void *) planstate;
+ }
+ 
+ /*
+  * pgsqlGetForeignPaths
+  *		Create possible scan paths for a scan on the foreign table
+  */
+ static void
+ pgsqlGetForeignPaths(PlannerInfo *root,
+ 					 RelOptInfo *baserel,
+ 					 Oid foreigntableid)
+ {
+ 	PgsqlFdwPlanState *planstate = (PgsqlFdwPlanState *) baserel->fdw_private;
+ 	List		   *fdw_private = NIL;
+ 	ForeignPath	   *path;
+ 
+ 	/*
+ 	 * Cost estimation should be modified to respect cost of establishing
+ 	 * connection and transferring data.
+ 	 */
+ 	adjust_costs(baserel->rows,
+ 				 baserel->width,
+ 				 &planstate->startup_cost,
+ 				 &planstate->total_cost);
+ 
+ 	/*
+ 	 * Create simplest ForeignScan path node, counterpart of SeqScan for
+ 	 * regular tables, for this scan, and add it to baserel.
+ 	 */
+ 	fdw_private = list_make1(makeString(planstate->sql));
+ 	path = create_foreignscan_path(root, baserel,
+ 								   baserel->rows,
+ 								   planstate->startup_cost,
+ 								   planstate->total_cost,
+ 								   NIL,				/* no pathkeys */
+ 								   NULL,			/* no outer rel either */
+ 								   NIL,				/* no param clause */
+ 								   fdw_private);	/* pass only simple SQL */
+ 	add_path(baserel, (Path *) path); 
+ 
+ 	/*
+ 	 * XXX We can consider sorted path here if we know that foreign table is
+ 	 * indexed on remote end.  For this purpose, should we support FOREIGN
+ 	 * INDEX to represent possible sets of sort keys which are relatively
+ 	 * efficient?
+ 	 */
+ }
+ 
+ /*
+  * pgsqlGetForeignPlan
+  *		Create ForeignScan plan node which implements selected best path
+  */
+ static ForeignScan *
+ pgsqlGetForeignPlan(PlannerInfo *root,
+ 					RelOptInfo *baserel,
+ 					Oid foreigntableid,
+ 					ForeignPath *best_path,
+ 					List *tlist,
+ 					List *scan_clauses)
+ {
+ 	Index			scan_relid = baserel->relid;
+ 	List		   *fdw_private = best_path->fdw_private;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	ListCell	   *lc;
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	DefElem		   *def;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 
+ 	/*
+ 	 * We have no native ability to evaluate restriction clauses, so we just
+ 	 * put all the scan_clauses into the plan node's qual list for the
+ 	 * executor to check.  So all we have to do here is strip RestrictInfo
+ 	 * nodes from the clauses and ignore pseudoconstants (which will be
+ 	 * handled elsewhere).
+ 	 */
+ 	scan_clauses = extract_actual_clauses(scan_clauses, false);
+ 
+ 	/*
+ 	 * Use specified fetch_count instead of default value, if any.  Foreign
+ 	 * table option overrides server option.
+ 	 */
+ 	table = GetForeignTable(foreigntableid);
+ 	foreach(lc, table->options)
+ 	{
+ 		def = (DefElem *) lfirst(lc);
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 			break;
+  
+ 	}
+ 	if (lc == NULL)
+ 	{
+ 		server = GetForeignServer(table->serverid);
+ 		foreach(lc, server->options)
+ 		{
+ 			def = (DefElem *) lfirst(lc);
+ 			if (strcmp(def->defname, "fetch_count") == 0)
+ 				break;
+ 	 
+ 		}
+ 	}
+ 	if (lc != NULL)
+ 		fetch_count = strtol(defGetString(def), NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * We store some more information in FdwPlan to pass them beyond the
+ 	 * boundary between planner and executor.  Finally FdwPlan using cursor
+ 	 * would hold items below:
+ 	 *
+ 	 * 1) plain SELECT statement (already added above)
+ 	 * 2) SQL statement used to declare cursor
+ 	 * 3) SQL statement used to fetch rows from cursor
+ 	 * 4) SQL statement used to reset cursor
+ 	 * 5) SQL statement used to close cursor
+ 	 *
+ 	 * These items are indexed with the enum FdwPrivateIndex, so an item
+ 	 * can be accessed directly via list_nth().  For example of FETCH
+ 	 * statement:
+ 	 *      list_nth(fdw_private, FdwPrivateFetchSql)
+ 	 */
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateSelectSql));
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Create the ForeignScan node with fdw_private of selected path. */
+ 	return make_foreignscan(tlist,
+ 							scan_clauses,
+ 							scan_relid,
+ 							NIL,
+ 							fdw_private);
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 
+ 	fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Estimate costs of executing given SQL statement.
+  */
+ static void
+ get_remote_estimate(const char *sql, PGconn *conn,
+ 					double *rows, int *width,
+ 					Cost *startup_cost, Cost *total_cost)
+ {
+ 	PGresult	   *res = NULL;
+ 	StringInfoData  buf;
+ 	char		   *plan;
+ 	char		   *p;
+ 	int				n;
+ 
+ 	/*
+ 	 * Construct EXPLAIN statement with given SQL statement.
+ 	 */
+ 	initStringInfo(&buf);
+ 	appendStringInfo(&buf, "EXPLAIN %s", sql);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, buf.data);
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK || PQntuples(res) == 0)
+ 		{
+ 			char *msg;
+ 
+ 			msg = pstrdup(PQerrorMessage(conn));
+ 			ereport(ERROR,
+ 					(errmsg("could not execute EXPLAIN for cost estimation"),
+ 					 errdetail("%s", msg),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/*
+ 		 * Find estimation portion from top plan node. Here we search opening
+ 		 * parentheses from the end of the line to avoid finding unexpected
+ 		 * parentheses.
+ 		 */
+ 		plan = PQgetvalue(res, 0, 0);
+ 		p = strrchr(plan, '(');
+ 		if (p == NULL)
+ 			elog(ERROR, "wrong EXPLAIN output: %s", plan);
+ 		n = sscanf(p,
+ 				   "(cost=%lf..%lf rows=%lf width=%d)",
+ 				   startup_cost, total_cost, rows, width);
+ 		if (n != 4)
+ 			elog(ERROR, "could not get estimation from EXPLAIN output");
+ 
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Adjust costs estimated on remote end with some overheads such as connection
+  * and data transfer.
+  */
+ static void
+ adjust_costs(double rows, int width, Cost *startup_cost, Cost *total_cost)
+ {
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * width * rows;
+ 	*total_cost += cpu_tuple_cost * rows;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	List		   *fdw_private;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...6eb99d5 .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,32 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "foreign/foreign.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSimpleSql(Oid relid,
+ 					   PlannerInfo *root,
+ 					   RelOptInfo *baserel,
+ 					   ForeignTable *table);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...b3fac96 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,248 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+ FETCH c;
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+ ERROR OUT;          -- ERROR
+ SELECT srvname FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...30fa7f5 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,261 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    If isolation level of local transaction is <literal>SERIALIZABLE</literal>,
+    <literal>SERIALIZABLE</literal> is used for remote transaction.  Otherwise,
+    if isolation level of local transaction is one of
+    <literal>READ UNCOMMITTED</literal>, <literal>READ COMMITTED</literal> or
+    <literal>REPEATABLE READ</literal>, then <literal>REPEATABLE READ</literal>
+    is used for remote transaction.
+    <literal>READ UNCOMMITTED</literal> and <literal>READ COMMITTED</literal>
+    are never used for remote transaction, because even
+    <literal>READ COMMITTED</literal> transaction might produce inconsistent
+    results, if remote data have been updated between two remote queries.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: DECLARE pgsql_fdw_cursor_3 SCROLL CURSOR FOR SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index beb62fe..a9585e9 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 14,19 ****
--- 14,21 ----
  
  #include "access/transam.h"
  #include "catalog/pg_class.h"
+ #include "catalog/pg_operator.h"
+ #include "catalog/pg_type.h"
  #include "commands/defrem.h"
  #include "foreign/foreign.h"
  #include "lib/stringinfo.h"
***************
*** 22,30 ****
--- 24,34 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/clauses.h"
  #include "optimizer/var.h"
+ #include "parser/parser.h"
  #include "parser/parsetree.h"
  #include "utils/builtins.h"
  #include "utils/lsyscache.h"
+ #include "utils/syscache.h"
  
  #include "pgsql_fdw.h"
  
*************** static void deparseRelation(StringInfo b
*** 44,49 ****
--- 48,81 ----
  							bool need_prefix);
  static void deparseVar(StringInfo buf, Var *node, PlannerInfo *root,
  					   RelOptInfo *baserel, bool need_prefix);
+ static void deparseConst(StringInfo buf, Const *node, PlannerInfo *root,
+ 						 RelOptInfo *baserel);
+ static void deparseBoolExpr(StringInfo buf, BoolExpr *node, PlannerInfo *root,
+ 							RelOptInfo *baserel);
+ static void deparseNullTest(StringInfo buf, NullTest *node, PlannerInfo *root,
+ 							RelOptInfo *baserel);
+ static void deparseDistinctExpr(StringInfo buf, DistinctExpr *node,
+ 								PlannerInfo *root, RelOptInfo *baserel);
+ static void deparseRelabelType(StringInfo buf, RelabelType *node,
+ 							   PlannerInfo *root, RelOptInfo *baserel);
+ static void deparseFuncExpr(StringInfo buf, FuncExpr *node, PlannerInfo *root,
+ 							RelOptInfo *baserel);
+ static void deparseParam(StringInfo buf, Param *node, PlannerInfo *root,
+ 						 RelOptInfo *baserel);
+ static void deparseScalarArrayOpExpr(StringInfo buf, ScalarArrayOpExpr *node,
+ 									 PlannerInfo *root, RelOptInfo *baserel);
+ static void deparseOpExpr(StringInfo buf, OpExpr *node, PlannerInfo *root,
+ 						  RelOptInfo *baserel);
+ static void deparseArrayRef(StringInfo buf, ArrayRef *node, PlannerInfo *root,
+ 							RelOptInfo *baserel);
+ static void deparseArrayExpr(StringInfo buf, ArrayExpr *node, PlannerInfo *root,							 RelOptInfo *baserel);
+ 
+ /*
+  * Determine whether an expression can be evaluated on remote side safely.
+  */
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
  
  /*
   * Deparse query representation into SQL statement which suits for remote
*************** deparseSimpleSql(Oid relid,
*** 152,157 ****
--- 184,268 ----
  }
  
  /*
+  * Examine baserestrictinfo of baserel, and extract expressions which can be
+  * evaluated on remote side safely.  This function never changes
+  * baserestrictinfo.
+  */
+ List *
+ extractRemoteExprs(Oid relid,
+ 				   PlannerInfo *root,
+ 				   RelOptInfo *baserel)
+ {
+ 	ListCell	   *lc;
+ 	List		   *exprs = NIL;
+ 
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo *ri = (RestrictInfo *) lfirst(lc);
+ 
+ 		if (is_foreign_expr(root, baserel, ri->clause))
+ 			exprs = lappend(exprs, ri->clause);
+ 	}
+ 
+ 	return exprs;
+ }
+ 
+ void
+ deparseExpr(StringInfo buf, Expr *node, PlannerInfo *root, RelOptInfo *baserel)
+ {
+ 	/*
+ 	 * This part must be match foreign_expr_walker.
+ 	 */
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 			deparseConst(buf, (Const *) node, root, baserel);
+ 			break;
+ 		case T_BoolExpr:
+ 			deparseBoolExpr(buf, (BoolExpr *) node, root, baserel);
+ 			break;
+ 		case T_NullTest:
+ 			deparseNullTest(buf, (NullTest *) node, root, baserel);
+ 			break;
+ 		case T_DistinctExpr:
+ 			deparseDistinctExpr(buf, (DistinctExpr *) node, root, baserel);
+ 			break;
+ 		case T_RelabelType:
+ 			deparseRelabelType(buf, (RelabelType *) node, root, baserel);
+ 			break;
+ 		case T_FuncExpr:
+ 			deparseFuncExpr(buf, (FuncExpr *) node, root, baserel);
+ 			break;
+ 		case T_Param:
+ 			deparseParam(buf, (Param *) node, root, baserel);
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			deparseScalarArrayOpExpr(buf, (ScalarArrayOpExpr *) node, root,
+ 									 baserel);
+ 			break;
+ 		case T_OpExpr:
+ 			deparseOpExpr(buf, (OpExpr *) node, root, baserel);
+ 			break;
+ 		case T_Var:
+ 			deparseVar(buf, (Var *) node, root, baserel, false);
+ 			break;
+ 		case T_ArrayRef:
+ 			deparseArrayRef(buf, (ArrayRef *) node, root, baserel);
+ 			break;
+ 		case T_ArrayExpr:
+ 			deparseArrayExpr(buf, (ArrayExpr *) node, root, baserel);
+ 			break;
+ 		default:
+ 			{
+ 				ereport(ERROR,
+ 						(errmsg("unsupported expression for deparse"),
+ 						 errdetail("%s", nodeToString(node))));
+ 			}
+ 			break;
+ 	}
+ }
+ 
+ /*
   * Deparse node into buf, with relation qualifier if need_prefix was true.  If
   * node is a column of a foreign table, use value of colname FDW option (if any)
   * instead of attribute name.
*************** deparseRelation(StringInfo buf,
*** 288,290 ****
--- 399,811 ----
  		appendStringInfo(buf, "%s.", q_nspname);
  	appendStringInfo(buf, "%s", q_relname);
  }
+ 
+ static void
+ deparseConst(StringInfo buf,
+ 			 Const *node,
+ 			 PlannerInfo *root,
+ 			 RelOptInfo *baserel)
+ {
+ 	Oid			typoutput;
+ 	bool		typIsVarlena;
+ 	char	   *extval;
+ 
+ 	if (node->constisnull)
+ 	{
+ 		appendStringInfo(buf, "NULL");
+ 		return;
+ 	}
+ 
+ 	getTypeOutputInfo(node->consttype,
+ 					  &typoutput, &typIsVarlena);
+ 	extval = OidOutputFunctionCall(typoutput, node->constvalue);
+ 
+ 	switch (node->consttype)
+ 	{
+ 		case INT2OID:
+ 		case INT4OID:
+ 		case INT8OID:
+ 		case OIDOID:
+ 		case FLOAT4OID:
+ 		case FLOAT8OID:
+ 		case NUMERICOID:
+ 			{
+ 				/*
+ 				 * No need to quote unless they contain special values such as
+ 				 * 'Nan'.
+ 				 */
+ 				if (strspn(extval, "0123456789+-eE.") == strlen(extval))
+ 				{
+ 					if (extval[0] == '+' || extval[0] == '-')
+ 						appendStringInfo(buf, "(%s)", extval);
+ 					else
+ 						appendStringInfoString(buf, extval);
+ 				}
+ 				else
+ 					appendStringInfo(buf, "'%s'", extval);
+ 			}
+ 			break;
+ 		case BITOID:
+ 		case VARBITOID:
+ 			appendStringInfo(buf, "B'%s'", extval);
+ 			break;
+ 		case BOOLOID:
+ 			if (strcmp(extval, "t") == 0)
+ 				appendStringInfoString(buf, "true");
+ 			else
+ 				appendStringInfoString(buf, "false");
+ 			break;
+ 
+ 		default:
+ 			{
+ 				const char *valptr;
+ 
+ 				appendStringInfoChar(buf, '\'');
+ 				for (valptr = extval; *valptr; valptr++)
+ 				{
+ 					char		ch = *valptr;
+ 
+ 					/*
+ 					 * standard_conforming_strings of remote session should be
+ 					 * set to similar value as local session.
+ 					 */
+ 					if (SQL_STR_DOUBLE(ch, !standard_conforming_strings))
+ 						appendStringInfoChar(buf, ch);
+ 					appendStringInfoChar(buf, ch);
+ 				}
+ 				appendStringInfoChar(buf, '\'');
+ 			}
+ 			break;
+ 	}
+ }
+ 
+ static void
+ deparseBoolExpr(StringInfo buf,
+ 				BoolExpr *node,
+ 				PlannerInfo *root,
+ 				RelOptInfo *baserel)
+ {
+ 	ListCell   *lc;
+ 	char	   *op;
+ 	bool		first;
+ 
+ 	switch (node->boolop)
+ 	{
+ 		case AND_EXPR:
+ 			op = "AND";
+ 			break;
+ 		case OR_EXPR:
+ 			op = "OR";
+ 			break;
+ 		case NOT_EXPR:
+ 			appendStringInfo(buf, "(NOT ");
+ 			deparseExpr(buf, list_nth(node->args, 0), root, baserel);
+ 			appendStringInfo(buf, ")");
+ 			return;
+ 	}
+ 
+ 	first = true;
+ 	appendStringInfo(buf, "(");
+ 	foreach(lc, node->args)
+ 	{
+ 		if (!first)
+ 			appendStringInfo(buf, " %s ", op);
+ 		deparseExpr(buf, (Expr *) lfirst(lc), root, baserel);
+ 		first = false;
+ 	}
+ 	appendStringInfo(buf, ")");
+ }
+ 
+ static void
+ deparseNullTest(StringInfo buf,
+ 				NullTest *node,
+ 				PlannerInfo *root,
+ 				RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "NullTest is not supported");
+ }
+ 
+ static void
+ deparseDistinctExpr(StringInfo buf,
+ 					DistinctExpr *node,
+ 					PlannerInfo *root,
+ 					RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "DistinctExpr not supported");
+ }
+ 
+ static void
+ deparseRelabelType(StringInfo buf,
+ 				   RelabelType *node,
+ 				   PlannerInfo *root,
+ 				   RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "RelabelType is not supported");
+ }
+ 
+ static void
+ deparseFuncExpr(StringInfo buf,
+ 				FuncExpr *node,
+ 				PlannerInfo *root,
+ 				RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "FuncExpr is not supported");
+ }
+ 
+ static void
+ deparseParam(StringInfo buf,
+ 			 Param *node,
+ 			 PlannerInfo *root,
+ 			 RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "Param is not supported");
+ }
+ 
+ static void
+ deparseScalarArrayOpExpr(StringInfo buf,
+ 						 ScalarArrayOpExpr *node,
+ 						 PlannerInfo *root,
+ 						 RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "ScalarArrayOpExpr is not supported");
+ }
+ 
+ static void
+ deparseOpExpr(StringInfo buf,
+ 			  OpExpr *node,
+ 			  PlannerInfo *root,
+ 			  RelOptInfo *baserel)
+ {
+ 	HeapTuple	tuple;
+ 	Form_pg_operator form;
+ 	char	   *opname;
+ 	char		oprkind;
+ 	ListCell   *arg = list_head(node->args);
+ 
+ 	/* Retieve necessary information about the operator from system catalog. */ 
+ 	tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(node->opno));
+ 	if (!HeapTupleIsValid(tuple))
+ 		elog(ERROR, "cache lookup failed for operator %u", node->opno);
+ 	form = (Form_pg_operator) GETSTRUCT(tuple);
+ 	opname = NameStr(form->oprname);
+ 	oprkind = form->oprkind;
+ 	ReleaseSysCache(tuple);
+ 
+ 	Assert((oprkind == 'r' && list_length(node->args) == 1) ||
+ 		   (oprkind == 'l' && list_length(node->args) == 1) ||
+ 		   (oprkind == 'b' && list_length(node->args) == 2));
+ 
+ 	appendStringInfo(buf, "(");
+ 	if (oprkind == 'b' || oprkind == 'r')
+ 	{
+ 		deparseExpr(buf, lfirst(arg), root, baserel);
+ 		arg = lnext(arg);
+ 	}
+ 
+ 	appendStringInfo(buf, " %s ", opname);
+ 
+ 	if (oprkind == 'b' || oprkind == 'r')
+ 		deparseExpr(buf, lfirst(arg), root, baserel);
+ 	appendStringInfo(buf, ")");
+ }
+ 
+ static void
+ deparseArrayRef(StringInfo buf,
+ 				ArrayRef *node,
+ 				PlannerInfo *root,
+ 				RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "ArrayRef is not supported");
+ }
+ 
+ static void
+ deparseArrayExpr(StringInfo buf,
+ 				 ArrayExpr *node,
+ 				 PlannerInfo *root,
+ 				 RelOptInfo *baserel)
+ {
+ 	elog(ERROR, "ArrayExpr is not supported");
+ }
+ 
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 		case T_BoolExpr:
+ 			break;
+ #ifdef NOT_SUPPORTED
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		/*
+ 		 * If function used by the expression is not built-in, it can't be
+ 		 * pushed down because it might has incompatible semantics on remote
+ 		 * side.
+ 		 */
+ 		case T_FuncExpr:
+ 			{
+ 				FuncExpr	   *fe = (FuncExpr *) node;
+ 				if (!is_builtin(fe->funcid))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ #endif
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ #ifdef NOT_SUPPORTED
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayRef *) node)->refelemtype))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ #endif
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index 5bac241..d60c768 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 230,241 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
     Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 230,241 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                                QUERY PLAN                                                               
! ----------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
     Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 101))
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 351,361 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  -- ===================================================================
--- 351,361 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                                QUERY PLAN                                                               
! ----------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = c2)
!    Remote SQL: DECLARE pgsql_fdw_cursor_19 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = c2))
  (3 rows)
  
  -- ===================================================================
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 364,380 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
           Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
!    ->  Materialize
!          ->  Foreign Scan on ft2 t2
!                Filter: (c1 = 2)
!                Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (8 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 364,379 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                                       QUERY PLAN                                                                       
! -------------------------------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
           Filter: (c1 = 1)
!          Remote SQL: DECLARE pgsql_fdw_cursor_20 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" = 1))
!    ->  Foreign Scan on ft2 t2
!          Filter: (c1 = 2)
!          Remote SQL: DECLARE pgsql_fdw_cursor_21 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" = 2))
! (7 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 391,410 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_26 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_27 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
  (12 rows)
  
  EXECUTE st2(10, 20);
--- 390,409 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                                QUERY PLAN                                                                               
! ------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_26 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" < 20))
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_27 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" > 10))
  (12 rows)
  
  EXECUTE st2(10, 20);
*************** EXECUTE st1(101, 101);
*** 422,441 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                     QUERY PLAN                                                                     
! ---------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_32 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_33 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
  (12 rows)
  
  EXECUTE st3(10, 20);
--- 421,440 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                                QUERY PLAN                                                                               
! ------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
                 Filter: (c1 < 20)
!                Remote SQL: DECLARE pgsql_fdw_cursor_32 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" < 20))
           ->  Hash
                 ->  HashAggregate
                       ->  Foreign Scan on ft2 t2
                             Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                            Remote SQL: DECLARE pgsql_fdw_cursor_33 SCROLL CURSOR FOR SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" > 10))
  (12 rows)
  
  EXECUTE st3(10, 20);
*************** EXECUTE st3(20, 30);
*** 453,503 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_38 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_39 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                     QUERY PLAN                                                     
! -------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = $1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_43 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (3 rows)
  
  -- cleanup
--- 452,502 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_38 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 1))
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_39 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 1))
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_40 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 1))
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_41 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 1))
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
     Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_42 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 1))
  (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: DECLARE pgsql_fdw_cursor_44 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" = 1))
  (3 rows)
  
  -- cleanup
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index 370d240..7746ab9 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
*************** typedef struct PgsqlFdwPlanState {
*** 75,80 ****
--- 75,84 ----
  	char		   *sql;
  	Cost			startup_cost;
  	Cost			total_cost;
+ 
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
  } PgsqlFdwPlanState;
  
  /*
*************** typedef struct PgsqlFdwPlanState {
*** 82,87 ****
--- 86,92 ----
   * stored in fdw_private list.
   */
  enum FdwPrivateIndex {
+ 	FdwPrivateFdwExprs,
  	FdwPrivateSelectSql,
  	FdwPrivateDeclareSql,
  	FdwPrivateFetchSql,
*************** pgsqlGetForeignRelSize(PlannerInfo *root
*** 268,273 ****
--- 273,281 ----
  	planstate->sql = sql;
  	planstate->startup_cost = startup_cost;
  	planstate->total_cost = total_cost;
+ 	planstate->table = table;
+ 	planstate->server = server;
+ 	planstate->user = user;
  	baserel->fdw_private = (void *) planstate;
  }
  
*************** pgsqlGetForeignPaths(PlannerInfo *root,
*** 283,288 ****
--- 291,305 ----
  	PgsqlFdwPlanState *planstate = (PgsqlFdwPlanState *) baserel->fdw_private;
  	List		   *fdw_private = NIL;
  	ForeignPath	   *path;
+ 	StringInfoData buf;
+ 	PGconn		   *conn;
+ 	double			rows;
+ 	int				width;
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ 	bool			first = true;
+ 	ListCell	   *lc;
+ 	List		   *fdw_exprs;
  
  	/*
  	 * Cost estimation should be modified to respect cost of establishing
*************** pgsqlGetForeignPaths(PlannerInfo *root,
*** 297,303 ****
  	 * Create simplest ForeignScan path node, counterpart of SeqScan for
  	 * regular tables, for this scan, and add it to baserel.
  	 */
! 	fdw_private = list_make1(makeString(planstate->sql));
  	path = create_foreignscan_path(root, baserel,
  								   baserel->rows,
  								   planstate->startup_cost,
--- 314,321 ----
  	 * Create simplest ForeignScan path node, counterpart of SeqScan for
  	 * regular tables, for this scan, and add it to baserel.
  	 */
! 	fdw_private = lappend(fdw_private, NIL);	/* no fdw_exprs */
! 	fdw_private = lappend(fdw_private, makeString(planstate->sql));
  	path = create_foreignscan_path(root, baserel,
  								   baserel->rows,
  								   planstate->startup_cost,
*************** pgsqlGetForeignPaths(PlannerInfo *root,
*** 309,314 ****
--- 327,389 ----
  	add_path(baserel, (Path *) path); 
  
  	/*
+ 	 * Create a ForeignScan path with WHERE push-down.
+ 	 */
+ 	fdw_exprs = extractRemoteExprs(foreigntableid, root, baserel);
+ 	if (fdw_exprs != NIL)
+ 	{
+ 		initStringInfo(&buf);
+ 		appendStringInfo(&buf, "%s WHERE (", planstate->sql);
+ 
+ 		foreach(lc, fdw_exprs)
+ 		{
+ 			Expr	   *expr = (Expr *) lfirst(lc);
+ 
+ 			/* Connect expressions with "AND". */
+ 			if (!first)
+ 				appendStringInfo(&buf, ") AND (");
+ 		
+ 			deparseExpr(&buf, expr, root, baserel);
+ 			first = false;
+ 		}
+ 		appendStringInfoChar(&buf, ')');
+ 
+ 		/*
+ 		 * Cost estimation should be modified to respect cost of establishing
+ 		 * connection and transferring data.
+ 		 */
+ 		conn = GetConnection(planstate->server, planstate->user, false);
+ 		get_remote_estimate(buf.data,
+ 							conn,
+ 							&rows,
+ 							&width,
+ 							&startup_cost,
+ 							&total_cost);
+ 		ReleaseConnection(conn);
+ 		adjust_costs(baserel->rows,
+ 					 baserel->width,
+ 					 &planstate->startup_cost,
+ 					 &planstate->total_cost);
+ 
+ 		/*
+ 		 * Create simplest ForeignScan path node, counterpart of SeqScan for
+ 		 * regular tables, for this scan, and add it to baserel.
+ 		 */
+ 		fdw_private = NIL;
+ 		fdw_private = lappend(fdw_private, fdw_exprs);
+ 		fdw_private = lappend(fdw_private, makeString(buf.data));
+ 		path = create_foreignscan_path(root, baserel,
+ 									   rows,
+ 									   startup_cost,
+ 									   total_cost,
+ 									   NIL,				/* no pathkeys */
+ 									   NULL,			/* no outer rel either */
+ 									   NIL,				/* no param clause */
+ 									   fdw_private);	/* pass SQL */
+ 		add_path(baserel, (Path *) path); 
+ 	}
+ 
+ 	/*
  	 * XXX We can consider sorted path here if we know that foreign table is
  	 * indexed on remote end.  For this purpose, should we support FOREIGN
  	 * INDEX to represent possible sets of sort keys which are relatively
*************** pgsqlGetForeignPlan(PlannerInfo *root,
*** 338,343 ****
--- 413,419 ----
  	DefElem		   *def;
  	int				fetch_count = DEFAULT_FETCH_COUNT;
  	char		   *sql;
+ 	List		   *fdw_exprs = NIL;
  
  	/*
  	 * We have no native ability to evaluate restriction clauses, so we just
*************** pgsqlGetForeignPlan(PlannerInfo *root,
*** 380,396 ****
  	 * boundary between planner and executor.  Finally FdwPlan using cursor
  	 * would hold items below:
  	 *
! 	 * 1) plain SELECT statement (already added above)
! 	 * 2) SQL statement used to declare cursor
! 	 * 3) SQL statement used to fetch rows from cursor
! 	 * 4) SQL statement used to reset cursor
! 	 * 5) SQL statement used to close cursor
  	 *
  	 * These items are indexed with the enum FdwPrivateIndex, so an item
  	 * can be accessed directly via list_nth().  For example of FETCH
  	 * statement:
  	 *      list_nth(fdw_private, FdwPrivateFetchSql)
  	 */
  	sql = strVal(list_nth(fdw_private, FdwPrivateSelectSql));
  
  	/* Construct cursor name from sequential value */
--- 456,474 ----
  	 * boundary between planner and executor.  Finally FdwPlan using cursor
  	 * would hold items below:
  	 *
! 	 * 1) expressions which are pushed down
! 	 * 2) plain SELECT statement (already added above)
! 	 * 3) SQL statement used to declare cursor
! 	 * 4) SQL statement used to fetch rows from cursor
! 	 * 5) SQL statement used to reset cursor
! 	 * 6) SQL statement used to close cursor
  	 *
  	 * These items are indexed with the enum FdwPrivateIndex, so an item
  	 * can be accessed directly via list_nth().  For example of FETCH
  	 * statement:
  	 *      list_nth(fdw_private, FdwPrivateFetchSql)
  	 */
+ 	fdw_exprs = list_nth(fdw_private, FdwPrivateFdwExprs);
  	sql = strVal(list_nth(fdw_private, FdwPrivateSelectSql));
  
  	/* Construct cursor name from sequential value */
*************** pgsqlGetForeignPlan(PlannerInfo *root,
*** 420,426 ****
  	return make_foreignscan(tlist,
  							scan_clauses,
  							scan_relid,
! 							NIL,
  							fdw_private);
  }
  
--- 498,504 ----
  	return make_foreignscan(tlist,
  							scan_clauses,
  							scan_relid,
! 							fdw_exprs,
  							fdw_private);
  }
  
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index 6eb99d5..b7d1310 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
*************** char *deparseSimpleSql(Oid relid,
*** 28,32 ****
--- 28,39 ----
  					   PlannerInfo *root,
  					   RelOptInfo *baserel,
  					   ForeignTable *table);
+ List *extractRemoteExprs(Oid relid,
+ 						 PlannerInfo *root,
+ 						 RelOptInfo *baserel);
+ void deparseExpr(StringInfo buf,
+ 				 Expr *expr,
+ 				 PlannerInfo *root,
+ 				 RelOptInfo *baserel);
  
  #endif /* PGSQL_FDW_H */

diff --git a/contrib/Makefile b/contrib/Makefile
index ac0a80a..14aa433 100644
*** a/contrib/Makefile
--- b/contrib/Makefile
*************** SUBDIRS = \
*** 41,46 ****
--- 41,47 ----
  		pgbench		\
  		pgcrypto	\
  		pgrowlocks	\
+ 		pgsql_fdw	\
  		pgstattuple	\
  		seg		\
  		spi		\
diff --git a/contrib/README b/contrib/README
index a1d42a1..d3fa211 100644
*** a/contrib/README
--- b/contrib/README
*************** pgrowlocks -
*** 158,163 ****
--- 158,167 ----
  	A function to return row locking information
  	by Tatsuo Ishii <ishii@sraoss.co.jp>
  
+ pgsql_fdw -
+ 	Foreign-data wrapper for external PostgreSQL servers.
+ 	by Shigeru Hanada <shigeru.hanada@gmail.com>
+ 
  pgstattuple -
  	Functions to return statistics about "dead" tuples and free
  	space within a table
diff --git a/contrib/pgsql_fdw/.gitignore b/contrib/pgsql_fdw/.gitignore
index ...0854728 .
*** a/contrib/pgsql_fdw/.gitignore
--- b/contrib/pgsql_fdw/.gitignore
***************
*** 0 ****
--- 1,4 ----
+ # Generated subdirectories
+ /results/
+ *.o
+ *.so
diff --git a/contrib/pgsql_fdw/Makefile b/contrib/pgsql_fdw/Makefile
index ...6381365 .
*** a/contrib/pgsql_fdw/Makefile
--- b/contrib/pgsql_fdw/Makefile
***************
*** 0 ****
--- 1,22 ----
+ # contrib/pgsql_fdw/Makefile
+ 
+ MODULE_big = pgsql_fdw
+ OBJS	= pgsql_fdw.o option.o deparse.o connection.o
+ PG_CPPFLAGS = -I$(libpq_srcdir)
+ SHLIB_LINK = $(libpq)
+ 
+ EXTENSION = pgsql_fdw
+ DATA = pgsql_fdw--1.0.sql
+ 
+ REGRESS = pgsql_fdw
+ 
+ ifdef USE_PGXS
+ PG_CONFIG = pg_config
+ PGXS := $(shell $(PG_CONFIG) --pgxs)
+ include $(PGXS)
+ else
+ subdir = contrib/pgsql_fdw
+ top_builddir = ../..
+ include $(top_builddir)/src/Makefile.global
+ include $(top_srcdir)/contrib/contrib-global.mk
+ endif
diff --git a/contrib/pgsql_fdw/connection.c b/contrib/pgsql_fdw/connection.c
index ...c971bd7 .
*** a/contrib/pgsql_fdw/connection.c
--- b/contrib/pgsql_fdw/connection.c
***************
*** 0 ****
--- 1,555 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.c
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/xact.h"
+ #include "catalog/pg_type.h"
+ #include "foreign/foreign.h"
+ #include "funcapi.h"
+ #include "libpq-fe.h"
+ #include "mb/pg_wchar.h"
+ #include "miscadmin.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
+ #include "utils/hsearch.h"
+ #include "utils/memutils.h"
+ #include "utils/resowner.h"
+ #include "utils/tuplestore.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ /* ============================================================================
+  * Connection management functions
+  * ==========================================================================*/
+ 
+ /*
+  * Connection cache entry managed with hash table.
+  */
+ typedef struct ConnCacheEntry
+ {
+ 	/* hash key must be first */
+ 	Oid				serverid;	/* oid of foreign server */
+ 	Oid				userid;		/* oid of local user */
+ 
+ 	bool			use_tx;		/* true when using remote transaction */
+ 	int				refs;		/* reference counter */
+ 	PGconn		   *conn;		/* foreign server connection */
+ } ConnCacheEntry;
+ 
+ /*
+  * Hash table which is used to cache connection to PostgreSQL servers, will be
+  * initialized before first attempt to connect PostgreSQL server by the backend.
+  */
+ static HTAB *FSConnectionHash;
+ 
+ /* ----------------------------------------------------------------------------
+  * prototype of private functions
+  * --------------------------------------------------------------------------*/
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg);
+ static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
+ static void begin_remote_tx(PGconn *conn);
+ static void abort_remote_tx(PGconn *conn);
+ 
+ /*
+  * Get a PGconn which can be used to execute foreign query on the remote
+  * PostgreSQL server with the user's authorization.  If this was the first
+  * request for the server, new connection is established.
+  *
+  * When use_tx is true, remote transaction is started if caller is the only
+  * user of the connection.  Isolation level of the remote transaction is same
+  * as local transaction, and remote transaction will be aborted when last
+  * user release.
+  *
+  * TODO: Note that caching connections requires a mechanism to detect change of
+  * FDW object to invalidate already established connections.
+  */
+ PGconn *
+ GetConnection(ForeignServer *server, UserMapping *user, bool use_tx)
+ {
+ 	bool			found;
+ 	ConnCacheEntry *entry;
+ 	ConnCacheEntry	key;
+ 
+ 	/* initialize connection cache if it isn't */
+ 	if (FSConnectionHash == NULL)
+ 	{
+ 		HASHCTL		ctl;
+ 
+ 		/* hash key is a pair of oids: serverid and userid */
+ 		MemSet(&ctl, 0, sizeof(ctl));
+ 		ctl.keysize = sizeof(Oid) + sizeof(Oid);
+ 		ctl.entrysize = sizeof(ConnCacheEntry);
+ 		ctl.hash = tag_hash;
+ 		ctl.match = memcmp;
+ 		ctl.keycopy = memcpy;
+ 		/* allocate FSConnectionHash in the cache context */
+ 		ctl.hcxt = CacheMemoryContext;
+ 		FSConnectionHash = hash_create("Foreign Connections", 32,
+ 									   &ctl,
+ 									   HASH_ELEM | HASH_CONTEXT |
+ 									   HASH_FUNCTION | HASH_COMPARE |
+ 									   HASH_KEYCOPY);
+ 	}
+ 
+ 	/* Create key value for the entry. */
+ 	MemSet(&key, 0, sizeof(key));
+ 	key.serverid = server->serverid;
+ 	key.userid = GetOuterUserId();
+ 
+ 	/*
+ 	 * Find cached entry for requested connection.  If we couldn't find,
+ 	 * callback function of ResourceOwner should be registered to clean the
+ 	 * connection up on error including user interrupt.
+ 	 */
+ 	entry = hash_search(FSConnectionHash, &key, HASH_ENTER, &found);
+ 	if (!found)
+ 	{
+ 		entry->refs = 0;
+ 		entry->use_tx = false;
+ 		entry->conn = NULL;
+ 		RegisterResourceReleaseCallback(cleanup_connection, entry);
+ 	}
+ 
+ 	/*
+ 	 * We don't check the health of cached connection here, because it would
+ 	 * require some overhead.  Broken connection and its cache entry will be
+ 	 * cleaned up when the connection is actually used.
+ 	 */
+ 
+ 	/*
+ 	 * If cache entry doesn't have connection, we have to establish new
+ 	 * connection.
+ 	 */
+ 	if (entry->conn == NULL)
+ 	{
+ 		/*
+ 		 * Use PG_TRY block to ensure closing connection on error.
+ 		 */
+ 		PG_TRY();
+ 		{
+ 			/*
+ 			 * Connect to the foreign PostgreSQL server, and store it in cache
+ 			 * entry to keep new connection.
+ 			 * Note: key items of entry has already been initialized in
+ 			 * hash_search(HASH_ENTER).
+ 			 */
+ 			entry->conn = connect_pg_server(server, user);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			/* Clear connection cache entry on error case. */
+ 			PQfinish(entry->conn);
+ 			entry->refs = 0;
+ 			entry->use_tx = false;
+ 			entry->conn = NULL;
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Increase connection reference counter. */
+ 	entry->refs++;
+ 
+ 	/*
+ 	 * If requester is the only referrer of this connection, start transaction
+ 	 * with the same isolation level as the local transaction we are in.
+ 	 * We need to remember whether this connection uses remote transaction to
+ 	 * abort it when this connection is released completely.
+ 	 */
+ 	if (use_tx && entry->refs == 1)
+ 		begin_remote_tx(entry->conn);
+ 	entry->use_tx = use_tx;
+ 
+ 
+ 	return entry->conn;
+ }
+ 
+ /*
+  * For non-superusers, insist that the connstr specify a password.	This
+  * prevents a password from being picked up from .pgpass, a service file,
+  * the environment, etc.  We don't want the postgres user's passwords
+  * to be accessible to non-superusers.
+  */
+ static void
+ check_conn_params(const char **keywords, const char **values)
+ {
+ 	int			i;
+ 
+ 	/* no check required if superuser */
+ 	if (superuser())
+ 		return;
+ 
+ 	/* ok if params contain a non-empty password */
+ 	for (i = 0; keywords[i] != NULL; i++)
+ 	{
+ 		if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
+ 			return;
+ 	}
+ 
+ 	ereport(ERROR,
+ 		  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 		   errmsg("password is required"),
+ 		   errdetail("Non-superusers must provide a password in the connection string.")));
+ }
+ 
+ static PGconn *
+ connect_pg_server(ForeignServer *server, UserMapping *user)
+ {
+ 	const char	   *conname = server->servername;
+ 	PGconn		   *conn;
+ 	const char	  **all_keywords;
+ 	const char	  **all_values;
+ 	const char	  **keywords;
+ 	const char	  **values;
+ 	int				n;
+ 	int				i, j;
+ 
+ 	/*
+ 	 * Construct connection params from generic options of ForeignServer and
+ 	 * UserMapping.  Those two object hold only libpq options.
+ 	 * Extra 3 items are for:
+ 	 *   *) fallback_application_name
+ 	 *   *) client_encoding
+ 	 *   *) NULL termination (end marker)
+ 	 *
+ 	 * Note: We don't omit any parameters even target database might be older
+ 	 * than local, because unexpected parameters are just ignored.
+ 	 */
+ 	n = list_length(server->options) + list_length(user->options) + 3;
+ 	all_keywords = (const char **) palloc(sizeof(char *) * n);
+ 	all_values = (const char **) palloc(sizeof(char *) * n);
+ 	keywords = (const char **) palloc(sizeof(char *) * n);
+ 	values = (const char **) palloc(sizeof(char *) * n);
+ 	n = 0;
+ 	n += ExtractConnectionOptions(server->options,
+ 								  all_keywords + n, all_values + n);
+ 	n += ExtractConnectionOptions(user->options,
+ 								  all_keywords + n, all_values + n);
+ 	all_keywords[n] = all_values[n] = NULL;
+ 
+ 	for (i = 0, j = 0; all_keywords[i]; i++)
+ 	{
+ 		keywords[j] = all_keywords[i];
+ 		values[j] = all_values[i];
+ 		j++;
+ 	}
+ 
+ 	/* Use "pgsql_fdw" as fallback_application_name. */
+ 	keywords[j] = "fallback_application_name";
+ 	values[j++] = "pgsql_fdw";
+ 
+ 	/* Set client_encoding so that libpq can convert encoding properly. */
+ 	keywords[j] = "client_encoding";
+ 	values[j++] = GetDatabaseEncodingName();
+ 
+ 	keywords[j] = values[j] = NULL;
+ 	pfree(all_keywords);
+ 	pfree(all_values);
+ 
+ 	/* verify connection parameters and do connect */
+ 	check_conn_params(keywords, values);
+ 	conn = PQconnectdbParams(keywords, values, 0);
+ 	if (!conn || PQstatus(conn) != CONNECTION_OK)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
+ 				 errmsg("could not connect to server \"%s\"", conname),
+ 				 errdetail("%s", PQerrorMessage(conn))));
+ 	pfree(keywords);
+ 	pfree(values);
+ 
+ 	/*
+ 	 * Check that non-superuser has used password to establish connection.
+ 	 * This check logic is based on dblink_security_check() in contrib/dblink.
+ 	 *
+ 	 * XXX Should we check this even if we don't provide unsafe version like
+ 	 * dblink_connect_u()?
+ 	 */
+ 	if (!superuser() && !PQconnectionUsedPassword(conn))
+ 	{
+ 		PQfinish(conn);
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+ 				 errmsg("password is required"),
+ 				 errdetail("Non-superuser cannot connect if the server does not request a password."),
+ 				 errhint("Target server's authentication method must be changed.")));
+ 	}
+ 
+ 	return conn;
+ }
+ 
+ /*
+  * Start transaction to use cursor to retrieve data separately.
+  */
+ static void
+ begin_remote_tx(PGconn *conn)
+ {
+ 	const char	   *sql = NULL;		/* keep compiler quiet. */
+ 	PGresult	   *res;
+ 
+ 	switch (XactIsoLevel)
+ 	{
+ 		case XACT_READ_UNCOMMITTED:
+ 		case XACT_READ_COMMITTED:
+ 		case XACT_REPEATABLE_READ:
+ 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ 			break;
+ 		case XACT_SERIALIZABLE:
+ 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ 			break;
+ 		default:
+ 			elog(ERROR, "unexpected isolation level: %d", XactIsoLevel);
+ 			break;
+ 	}
+ 
+ 	elog(DEBUG3, "starting remote transaction with \"%s\"", sql);
+ 
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not start transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ static void
+ abort_remote_tx(PGconn *conn)
+ {
+ 	PGresult	   *res;
+ 
+ 	elog(DEBUG3, "aborting remote transaction");
+ 
+ 	res = PQexec(conn, "ABORT TRANSACTION");
+ 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 	{
+ 		PQclear(res);
+ 		elog(ERROR, "could not abort transaction: %s", PQerrorMessage(conn));
+ 	}
+ 	PQclear(res);
+ }
+ 
+ /*
+  * Mark the connection as "unused", and close it if the caller was the last
+  * user of the connection.
+  */
+ void
+ ReleaseConnection(PGconn *conn)
+ {
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 
+ 	if (conn == NULL)
+ 		return;
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	hash_seq_init(&scan, FSConnectionHash);
+ 	while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 	{
+ 		if (entry->conn == conn)
+ 		{
+ 			hash_seq_term(&scan);
+ 			break;
+ 		}
+ 	}
+ 
+ 	/* If the released connection was an orphan, just close it. */
+ 	if (entry == NULL)
+ 	{
+ 		PQfinish(conn);
+ 		return;
+ 	}
+ 
+ 	/*
+ 	 * If this connection uses remote transaction and caller is the last user,
+ 	 * abort remote transaction and forget about it.
+ 	 */
+ 	if (entry->use_tx && entry->refs == 1)
+ 	{
+ 		abort_remote_tx(conn);
+ 		entry->use_tx = false;
+ 	}
+ 
+ 	/*
+ 	 * Decrease reference counter of this connection.  Even if the caller was
+ 	 * the last referrer, we don't unregister it from cache.
+ 	 */
+ 	entry->refs--;
+ }
+ 
+ /*
+  * Clean the connection up via ResourceOwner.
+  */
+ static void
+ cleanup_connection(ResourceReleasePhase phase,
+ 				   bool isCommit,
+ 				   bool isTopLevel,
+ 				   void *arg)
+ {
+ 	ConnCacheEntry *entry = (ConnCacheEntry *) arg;
+ 
+ 	/* If the transaction was committed, don't close connections. */
+ 	if (isCommit)
+ 		return;
+ 
+ 	/*
+ 	 * We clean the connection up on post-lock because foreign connections are
+ 	 * backend-internal resource.
+ 	 */
+ 	if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+ 		return;
+ 
+ 	/*
+ 	 * We ignore cleanup for ResourceOwners other than transaction.  At this
+ 	 * point, such a ResourceOwner is only Portal.
+ 	 */
+ 	if (CurrentResourceOwner != CurTransactionResourceOwner)
+ 		return;
+ 
+ 	/*
+ 	 * We don't need to clean up at end of subtransactions, because they might
+ 	 * be recovered to consistent state with savepoints.
+ 	 */
+ 	if (!isTopLevel)
+ 		return;
+ 
+ 	/*
+ 	 * Here, it must be after abort of top level transaction.  Disconnect and
+ 	 * forget every referrer.
+ 	 */
+ 	if (entry->conn != NULL)
+ 	{
+ 		PQfinish(entry->conn);
+ 		entry->refs = 0;
+ 		entry->conn = NULL;
+ 	}
+ }
+ 
+ /*
+  * Get list of connections currently active.
+  */
+ Datum pgsql_fdw_get_connections(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_get_connections);
+ Datum
+ pgsql_fdw_get_connections(PG_FUNCTION_ARGS)
+ {
+ 	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ 	HASH_SEQ_STATUS		scan;
+ 	ConnCacheEntry	   *entry;
+ 	MemoryContext		oldcontext = CurrentMemoryContext;
+ 	Tuplestorestate	   *tuplestore;
+ 	TupleDesc			tupdesc;
+ 
+ 	/* We return list of connection with storing them in a Tuplestore. */
+ 	rsinfo->returnMode = SFRM_Materialize;
+ 	rsinfo->setResult = NULL;
+ 	rsinfo->setDesc = NULL;
+ 
+ 	/* Create tuplestore and copy of TupleDesc in per-query context. */
+ 	MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
+ 
+ 	tupdesc = CreateTemplateTupleDesc(2, false);
+ 	TupleDescInitEntry(tupdesc, 1, "srvid", OIDOID, -1, 0);
+ 	TupleDescInitEntry(tupdesc, 2, "usesysid", OIDOID, -1, 0);
+ 	rsinfo->setDesc = tupdesc;
+ 
+ 	tuplestore = tuplestore_begin_heap(false, false, work_mem);
+ 	rsinfo->setResult = tuplestore;
+ 
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * We need to scan sequentially since we use the address to find
+ 	 * appropriate PGconn from the hash table.
+ 	 */
+ 	if (FSConnectionHash != NULL)
+ 	{
+ 		hash_seq_init(&scan, FSConnectionHash);
+ 		while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ 		{
+ 			Datum		values[2];
+ 			bool		nulls[2];
+ 			HeapTuple	tuple;
+ 
+ 			/* Ignore inactive connections */
+ 			if (PQstatus(entry->conn) != CONNECTION_OK)
+ 				continue;
+ 
+ 			/*
+ 			 * Ignore other users' connections if current user isn't a
+ 			 * superuser.
+ 			 */
+ 			if (!superuser() && entry->userid != GetUserId())
+ 				continue;
+ 
+ 			values[0] = ObjectIdGetDatum(entry->serverid);
+ 			values[1] = ObjectIdGetDatum(entry->userid);
+ 			nulls[0] = false;
+ 			nulls[1] = false;
+ 
+ 			tuple = heap_formtuple(tupdesc, values, nulls);
+ 			tuplestore_puttuple(tuplestore, tuple);
+ 		}
+ 	}
+ 	tuplestore_donestoring(tuplestore);
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Discard persistent connection designated by given connection name.
+  */
+ Datum pgsql_fdw_disconnect(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_disconnect);
+ Datum
+ pgsql_fdw_disconnect(PG_FUNCTION_ARGS)
+ {
+ 	Oid					serverid = PG_GETARG_OID(0);
+ 	Oid					userid = PG_GETARG_OID(1);
+ 	ConnCacheEntry		key;
+ 	ConnCacheEntry	   *entry = NULL;
+ 	bool				found;
+ 
+ 	/* Non-superuser can't discard other users' connection. */
+ 	if (!superuser() && userid != GetOuterUserId())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ 				 errmsg("only superuser can discard other user's connection")));
+ 
+ 	/*
+ 	 * If no connection has been established, or no such connections, just
+ 	 * return "NG" to indicate nothing has done.
+ 	 */
+ 	if (FSConnectionHash == NULL)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	key.serverid = serverid;
+ 	key.userid = userid;
+ 	entry = hash_search(FSConnectionHash, &key, HASH_FIND, &found);
+ 	if (!found)
+ 		PG_RETURN_TEXT_P(cstring_to_text("NG"));
+ 
+ 	/* Discard cached connection, and clear reference counter. */
+ 	PQfinish(entry->conn);
+ 	entry->refs = 0;
+ 	entry->conn = NULL;
+ 
+ 	PG_RETURN_TEXT_P(cstring_to_text("OK"));
+ }
diff --git a/contrib/pgsql_fdw/connection.h b/contrib/pgsql_fdw/connection.h
index ...4427f56 .
*** a/contrib/pgsql_fdw/connection.h
--- b/contrib/pgsql_fdw/connection.h
***************
*** 0 ****
--- 1,25 ----
+ /*-------------------------------------------------------------------------
+  *
+  * connection.h
+  *		  Connection management for pgsql_fdw
+  *
+  * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/connection.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ #ifndef CONNECTION_H
+ #define CONNECTION_H
+ 
+ #include "foreign/foreign.h"
+ #include "libpq-fe.h"
+ 
+ /*
+  * Connection management
+  */
+ PGconn *GetConnection(ForeignServer *server, UserMapping *user, bool use_tx);
+ void ReleaseConnection(PGconn *conn);
+ 
+ #endif /* CONNECTION_H */
diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ...ca3356d .
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 0 ****
--- 1,289 ----
+ /*-------------------------------------------------------------------------
+  *
+  * deparse.c
+  *		  query deparser for PostgreSQL
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/deparse.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/transam.h"
+ #include "catalog/pg_class.h"
+ #include "commands/defrem.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "nodes/nodeFuncs.h"
+ #include "nodes/nodes.h"
+ #include "nodes/makefuncs.h"
+ #include "optimizer/clauses.h"
+ #include "optimizer/var.h"
+ #include "parser/parsetree.h"
+ #include "utils/builtins.h"
+ #include "utils/lsyscache.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * Context for walk-through the expression tree.
+  */
+ typedef struct foreign_executable_cxt
+ {
+ 	PlannerInfo	   *root;
+ 	RelOptInfo	   *foreignrel;
+ } foreign_executable_cxt;
+ 
+ /*
+  * Get string representation which can be used in SQL statement from a node.
+  */
+ static void deparseRelation(StringInfo buf, Oid relid, PlannerInfo *root,
+ 							bool need_prefix);
+ static void deparseVar(StringInfo buf, Var *node, PlannerInfo *root,
+ 					   bool need_prefix);
+ 
+ /*
+  * Deparse query representation into SQL statement which suits for remote
+  * PostgreSQL server.  This function just creates simple query string which
+  * consists of only SELECT and FROM clause.
+  */
+ char *
+ deparseSimpleSql(Oid relid,
+ 			     PlannerInfo *root,
+ 			     RelOptInfo *baserel,
+ 			     ForeignTable *table)
+ {
+ 	StringInfoData	foreign_relname;
+ 	StringInfoData	sql;			/* builder for SQL statement */
+ 	bool		first;
+ 	AttrNumber	attr;
+ 	List	   *attr_used = NIL;	/* List of AttNumber used in the query */
+ 
+ 	initStringInfo(&sql);
+ 	initStringInfo(&foreign_relname);
+ 
+ 	/*
+ 	 * First of all, determine which column should be retrieved for this scan.
+ 	 *
+ 	 * We do this before deparsing SELECT clause because attributes which are
+ 	 * not used in neither reltargetlist nor baserel->baserestrictinfo, quals
+ 	 * evaluated on local, can be replaced with literal "NULL" in the SELECT
+ 	 * clause to reduce overhead of tuple handling tuple and data transfer.
+ 	 */
+ 	if (baserel->baserestrictinfo != NIL)
+ 	{
+ 		ListCell   *lc;
+ 
+ 		foreach (lc, baserel->baserestrictinfo)
+ 		{
+ 			RestrictInfo   *ri = (RestrictInfo *) lfirst(lc);
+ 			List		   *attrs;
+ 
+ 			/*
+ 			 * We need to know which attributes are used in qual evaluated
+ 			 * on the local server, because they should be listed in the
+ 			 * SELECT clause of remote query.  We can ignore attributes
+ 			 * which are referenced only in ORDER BY/GROUP BY clause because
+ 			 * such attributes has already been kept in reltargetlist.
+ 			 */
+ 			attrs = pull_var_clause((Node *) ri->clause,
+ 									PVC_RECURSE_AGGREGATES,
+ 									PVC_RECURSE_PLACEHOLDERS);
+ 			attr_used = list_union(attr_used, attrs);
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * deparse SELECT clause
+ 	 *
+ 	 * List attributes which are in either target list or local restriction.
+ 	 * Unused attributes are replaced with a literal "NULL" for optimization.
+ 	 *
+ 	 * Note that nothing is added for dropped columns, though tuple constructor
+ 	 * function requires entries for dropped columns.  Such entries must be
+ 	 * initialized with NULL before calling tuple constructor.
+ 	 */
+ 	appendStringInfo(&sql, "SELECT ");
+ 	attr_used = list_union(attr_used, baserel->reltargetlist);
+ 	first = true;
+ 	for (attr = 1; attr <= baserel->max_attr; attr++)
+ 	{
+ 		RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
+ 		Var		   *var = NULL;
+ 		ListCell   *lc;
+ 
+ 		/* Ignore dropped attributes. */
+ 		if (get_rte_attribute_is_dropped(rte, attr))
+ 			continue;
+ 
+ 		if (!first)
+ 			appendStringInfo(&sql, ", ");
+ 		first = false;
+ 
+ 		/*
+ 		 * We use linear search here, but it wouldn't be problem since
+ 		 * attr_used seems to not become so large.
+ 		 */
+ 		foreach (lc, attr_used)
+ 		{
+ 			var = lfirst(lc);
+ 			if (var->varattno == attr)
+ 				break;
+ 			var = NULL;
+ 		}
+ 		if (var != NULL)
+ 			deparseVar(&sql, var, root, false);
+ 		else
+ 			appendStringInfo(&sql, "NULL");
+ 	}
+ 	appendStringInfoChar(&sql, ' ');
+ 
+ 	/*
+ 	 * deparse FROM clause, including alias if any
+ 	 */
+ 	appendStringInfo(&sql, "FROM ");
+ 	deparseRelation(&sql, table->relid, root, true);
+ 
+ 	elog(DEBUG3, "Remote SQL: %s", sql.data);
+ 	return sql.data;
+ }
+ 
+ /*
+  * Deparse node into buf, with relation qualifier if need_prefix was true.  If
+  * node is a column of a foreign table, use value of colname FDW option (if any)
+  * instead of attribute name.
+  */
+ static void
+ deparseVar(StringInfo buf,
+ 		   Var *node,
+ 		   PlannerInfo *root,
+ 		   bool need_prefix)
+ {
+ 	RangeTblEntry  *rte;
+ 	char		   *colname = NULL;
+ 	const char	   *q_colname = NULL;
+ 	List		   *options;
+ 	ListCell	   *lc;
+ 
+ 	/* node must not be any of OUTER_VAR,INNER_VAR and INDEX_VAR. */
+ 	Assert(node->varno >= 1 && node->varno <= root->simple_rel_array_size);
+ 
+ 	/* Get RangeTblEntry from array in PlannerInfo. */
+ 	rte = root->simple_rte_array[node->varno];
+ 
+ 	/*
+ 	 * If the node is a column of a foreign table, and it has colname FDW
+ 	 * option, use its value.
+ 	 */
+ 	if (rte->relkind == RELKIND_FOREIGN_TABLE)
+ 	{
+ 		options = GetForeignColumnOptions(rte->relid, node->varattno);
+ 		foreach(lc, options)
+ 		{
+ 			DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 			if (strcmp(def->defname, "colname") == 0)
+ 			{
+ 				colname = defGetString(def);
+ 				break;
+ 			}
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * If the node refers a column of a regular table or it doesn't have colname
+ 	 * FDW option, use attribute name.
+ 	 */
+ 	if (colname == NULL)
+ 		colname = get_attname(rte->relid, node->varattno);
+ 
+ 	if (need_prefix)
+ 	{
+ 		char *aliasname;
+ 		const char *q_aliasname;
+ 
+ 		if (rte->eref != NULL && rte->eref->aliasname != NULL)
+ 			aliasname = rte->eref->aliasname;
+ 		else if (rte->alias != NULL && rte->alias->aliasname != NULL)
+ 			aliasname = rte->alias->aliasname;
+ 
+ 		q_aliasname = quote_identifier(aliasname);
+ 		appendStringInfo(buf, "%s.", q_aliasname);
+ 	}
+ 
+ 	q_colname = quote_identifier(colname);
+ 	appendStringInfo(buf, "%s", q_colname);
+ }
+ 
+ /*
+  * Deparse table which has relid as oid into buf, with schema qualifier if
+  * need_prefix was true.  If relid points a foreign table, use value of relname
+  * FDW option (if any) instead of relation's name.  Similarly, nspname FDW
+  * option overrides schema name.
+  */
+ static void
+ deparseRelation(StringInfo buf,
+ 				Oid relid,
+ 				PlannerInfo *root,
+ 				bool need_prefix)
+ {
+ 	int			i;
+ 	RangeTblEntry *rte = NULL;
+ 	ListCell   *lc;
+ 	const char *nspname = NULL;		/* plain namespace name */
+ 	const char *relname = NULL;		/* plain relation name */
+ 	const char *q_nspname;			/* quoted namespace name */
+ 	const char *q_relname;			/* quoted relation name */
+ 
+ 	/* Find RangeTblEntry for the relation from PlannerInfo. */
+ 	for (i = 1; i < root->simple_rel_array_size; i++)
+ 	{
+ 		if (root->simple_rte_array[i]->relid == relid)
+ 		{
+ 			rte = root->simple_rte_array[i];
+ 			break;
+ 		}
+ 	}
+ 	if (rte == NULL)
+ 		elog(ERROR, "relation with OID %u is not used in the query", relid);
+ 
+ 	/* If target is a foreign table, obtain additional catalog information. */
+ 	if (rte->relkind == RELKIND_FOREIGN_TABLE)
+ 	{
+ 		ForeignTable *table = GetForeignTable(rte->relid);
+ 
+ 		/*
+ 		 * Use value of FDW options if any, instead of the name of object
+ 		 * itself.
+ 		 */
+ 		foreach(lc, table->options)
+ 		{
+ 			DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 			if (need_prefix && strcmp(def->defname, "nspname") == 0)
+ 				nspname = defGetString(def);
+ 			else if (strcmp(def->defname, "relname") == 0)
+ 				relname = defGetString(def);
+ 		}
+ 	}
+ 
+ 	/* Quote each identifier, if necessary. */
+ 	if (need_prefix)
+ 	{
+ 		if (nspname == NULL)
+ 			nspname = get_namespace_name(get_rel_namespace(relid));
+ 		q_nspname = quote_identifier(nspname);
+ 	}
+ 
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	q_relname = quote_identifier(relname);
+ 
+ 	/* Construct relation reference into the buffer. */
+ 	if (need_prefix)
+ 		appendStringInfo(buf, "%s.", q_nspname);
+ 	appendStringInfo(buf, "%s", q_relname);
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index ...fdd908c .
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
***************
*** 0 ****
--- 1,589 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ -- Clean up in case a prior regression run failed
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ RESET client_min_messages;
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ CREATE EXTENSION pgsql_fdw;
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "T 1"
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for table "T 2"
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: 
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ERROR:  invalid option "user"
+ HINT:  Valid options in this context are: authtype, service, connect_timeout, dbname, host, hostaddr, port, tty, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, requiressl, sslcompression, sslmode, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, fetch_count
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ERROR:  invalid option "host"
+ HINT:  Valid options in this context are: user, password
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: nspname, relname, fetch_count
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ERROR:  invalid value for fetch_count: "a"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ERROR:  invalid value for fetch_count: "0"
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ERROR:  invalid value for fetch_count: "-1"
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ERROR:  invalid option "invalid"
+ HINT:  Valid options in this context are: colname
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+                                             List of foreign-data wrappers
+    Name    |     Owner      |      Handler      |      Validator      | Access privileges | FDW Options | Description 
+ -----------+----------------+-------------------+---------------------+-------------------+-------------+-------------
+  pgsql_fdw | pgsql_fdw_user | pgsql_fdw_handler | pgsql_fdw_validator |                   |             | 
+ (1 row)
+ 
+ \des+
+                                                                                                                                                                                                                               List of foreign servers
+    Name    |     Owner      | Foreign-data wrapper | Access privileges | Type | Version |                                                                                                                                                                                 FDW Options                                                                                                                                                                                 | Description 
+ -----------+----------------+----------------------+-------------------+------+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------
+  loopback1 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (authtype 'value', service 'value', connect_timeout 'value', dbname 'value', host 'value', hostaddr 'value', port 'value', tty 'value', options 'value', application_name 'value', keepalives 'value', keepalives_idle 'value', keepalives_interval 'value', sslcompression 'value', sslmode 'value', sslcert 'value', sslkey 'value', sslrootcert 'value', sslcrl 'value') | 
+  loopback2 | pgsql_fdw_user | pgsql_fdw            |                   |      |         | (dbname 'contrib_regression', fetch_count '2')                                                                                                                                                                                                                                                                                                                              | 
+ (2 rows)
+ 
+ \deu+
+           List of user mappings
+   Server   |   User name    | FDW Options 
+ -----------+----------------+-------------
+  loopback1 | public         | 
+  loopback2 | pgsql_fdw_user | 
+ (2 rows)
+ 
+ \det+
+                                     List of foreign tables
+  Schema | Table |  Server   |                    FDW Options                    | Description 
+ --------+-------+-----------+---------------------------------------------------+-------------
+  public | ft1   | loopback2 | (nspname 'S 1', relname 'T 1')                    | 
+  public | ft2   | loopback2 | (nspname 'S 1', relname 'T 1', fetch_count '100') | 
+ (2 rows)
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: ft1.c3, ft1.c1
+          ->  Foreign Scan on public.ft1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_0 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+                                                           QUERY PLAN                                                          
+ ------------------------------------------------------------------------------------------------------------------------------
+  Limit
+    Output: c1, c2, c3, c4, c5, c6, c7
+    ->  Sort
+          Output: c1, c2, c3, c4, c5, c6, c7
+          Sort Key: t1.c3, t1.c1
+          ->  Foreign Scan on public.ft1 t1
+                Output: c1, c2, c3, c4, c5, c6, c7
+                Remote SQL: DECLARE pgsql_fdw_cursor_2 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (8 rows)
+ 
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+  102 |  2 | 00102 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+  103 |  3 | 00103 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+  104 |  4 | 00104 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+  105 |  5 | 00105 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+  106 |  6 | 00106 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+  107 |  7 | 00107 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+  108 |  8 | 00108 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+  109 |  9 | 00109 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  110 |  0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+                                                     QUERY PLAN                                                    
+ ------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7
+    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
+    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (4 rows)
+ 
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+  c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ -----+----+-------+------------------------------+--------------------------+----+------------
+  101 |  1 | 00101 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+  count 
+ -------
+   1000
+ (1 row)
+ 
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+  c1  
+ -----
+  101
+  102
+  103
+  104
+  105
+  106
+  107
+  108
+  109
+  110
+ (10 rows)
+ 
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST | Sun Jan 04 00:00:00 1970 | 3  | 3         
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4  | 4         
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST | Tue Jan 06 00:00:00 1970 | 5  | 5         
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST | Wed Jan 07 00:00:00 1970 | 6  | 6         
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST | Thu Jan 08 00:00:00 1970 | 7  | 7         
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST | Fri Jan 09 00:00:00 1970 | 8  | 8         
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST | Sat Jan 10 00:00:00 1970 | 9  | 9         
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0  | 0         
+ (10 rows)
+ 
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+   c1  | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ------+----+-------+------------------------------+--------------------------+----+------------
+  1000 |  0 | 01000 | Thu Jan 01 00:00:00 1970 PST | Thu Jan 01 00:00:00 1970 | 0  | 0         
+ (1 row)
+ 
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+  c1 | c2 |  c3   |              c4              
+ ----+----+-------+------------------------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST
+   3 |  3 | 00003 | Sun Jan 04 00:00:00 1970 PST
+   4 |  4 | 00004 | Mon Jan 05 00:00:00 1970 PST
+   5 |  5 | 00005 | Tue Jan 06 00:00:00 1970 PST
+   6 |  6 | 00006 | Wed Jan 07 00:00:00 1970 PST
+   7 |  7 | 00007 | Thu Jan 08 00:00:00 1970 PST
+   8 |  8 | 00008 | Fri Jan 09 00:00:00 1970 PST
+   9 |  9 | 00009 | Sat Jan 10 00:00:00 1970 PST
+  10 |  0 | 00010 | Sun Jan 11 00:00:00 1970 PST
+ (10 rows)
+ 
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+  ?column? | ?column? 
+ ----------+----------
+  fixed    | 
+ (1 row)
+ 
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = pgsql_fdw_abs(c2))
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 === c2)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = abs(c2))
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = c2)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+                                      QUERY PLAN                                      
+ -------------------------------------------------------------------------------------
+  Nested Loop
+    ->  Foreign Scan on ft1 t1
+          Filter: (c1 = 1)
+          Remote SQL: SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+    ->  Foreign Scan on ft2 t2
+          Filter: (c1 = 2)
+          Remote SQL: SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
+ (7 rows)
+ 
+ EXECUTE st1(1, 1);
+   c3   |  c3   
+ -------+-------
+  00001 | 00001
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+                                            QUERY PLAN                                           
+ ------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Semi Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  Foreign Scan on ft2 t2
+                      Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
+                      Remote SQL: SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
+ (11 rows)
+ 
+ EXECUTE st2(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st1(101, 101);
+   c3   |  c3   
+ -------+-------
+  00101 | 00101
+ (1 row)
+ 
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+                                            QUERY PLAN                                           
+ ------------------------------------------------------------------------------------------------
+  Sort
+    Sort Key: t1.c1
+    ->  Hash Semi Join
+          Hash Cond: (t1.c3 = t2.c3)
+          ->  Foreign Scan on ft1 t1
+                Filter: (c1 < 20)
+                Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+          ->  Hash
+                ->  Foreign Scan on ft2 t2
+                      Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
+                      Remote SQL: SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
+ (11 rows)
+ 
+ EXECUTE st3(10, 20);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  16 |  6 | 00016 | Sat Jan 17 00:00:00 1970 PST | Sat Jan 17 00:00:00 1970 | 6  | 6         
+ (1 row)
+ 
+ EXECUTE st3(20, 30);
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+  23 |  3 | 00023 | Sat Jan 24 00:00:00 1970 PST | Sat Jan 24 00:00:00 1970 | 3  | 3         
+ (1 row)
+ 
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = 1)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+                              QUERY PLAN                              
+ ---------------------------------------------------------------------
+  Foreign Scan on ft1 t1
+    Filter: (c1 = $1)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
+ (3 rows)
+ 
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+   srvname  |    usename     
+ -----------+----------------
+  loopback2 | pgsql_fdw_user
+ (1 row)
+ 
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+  pgsql_fdw_disconnect 
+ ----------------------
+  OK
+ (1 row)
+ 
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+  srvname | usename 
+ ---------+---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1         
+ (1 row)
+ 
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ FETCH c;
+  c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
+ ----+----+-------+------------------------------+--------------------------+----+------------
+   2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2         
+ (1 row)
+ 
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+   srvname  
+ -----------
+  loopback2
+ (1 row)
+ 
+ ERROR OUT;          -- ERROR
+ ERROR:  syntax error at or near "ERROR"
+ LINE 1: ERROR OUT;
+         ^
+ SELECT srvname FROM pgsql_fdw_connections;
+  srvname 
+ ---------
+ (0 rows)
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ NOTICE:  drop cascades to 2 other objects
+ DETAIL:  drop cascades to table "S 1"."T 1"
+ drop cascades to table "S 1"."T 2"
+ DROP EXTENSION pgsql_fdw CASCADE;
+ NOTICE:  drop cascades to 6 other objects
+ DETAIL:  drop cascades to server loopback1
+ drop cascades to user mapping for public
+ drop cascades to server loopback2
+ drop cascades to user mapping for pgsql_fdw_user
+ drop cascades to foreign table ft1
+ drop cascades to foreign table ft2
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/contrib/pgsql_fdw/option.c b/contrib/pgsql_fdw/option.c
index ...a2a8927 .
*** a/contrib/pgsql_fdw/option.c
--- b/contrib/pgsql_fdw/option.c
***************
*** 0 ****
--- 1,242 ----
+ /*-------------------------------------------------------------------------
+  *
+  * option.c
+  *		  FDW option handling
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/option.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ 
+ #include "access/reloptions.h"
+ #include "catalog/pg_foreign_data_wrapper.h"
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "catalog/pg_user_mapping.h"
+ #include "commands/defrem.h"
+ #include "fmgr.h"
+ #include "foreign/foreign.h"
+ #include "lib/stringinfo.h"
+ #include "miscadmin.h"
+ 
+ #include "pgsql_fdw.h"
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_validator(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_validator);
+ 
+ /*
+  * Describes the valid options for objects that use this wrapper.
+  */
+ typedef struct PgsqlFdwOption
+ {
+ 	const char *optname;
+ 	Oid			optcontext;		/* Oid of catalog in which options may appear */
+ 	bool		is_libpq_opt;	/* true if it's used in libpq */
+ } PgsqlFdwOption;
+ 
+ /*
+  * Valid options for pgsql_fdw.
+  */
+ static PgsqlFdwOption valid_options[] = {
+ 
+ 	/*
+ 	 * Options for libpq connection.
+ 	 * Note: This list should be updated along with PQconninfoOptions in
+ 	 * interfaces/libpq/fe-connect.c, so the order is kept as is.
+ 	 *
+ 	 * Some useless libpq connection options are not accepted by pgsql_fdw:
+ 	 *   client_encoding: set to local database encoding automatically
+ 	 *   fallback_application_name: fixed to "pgsql_fdw"
+ 	 *   replication: pgsql_fdw never be replication client
+ 	 */
+ 	{"authtype", ForeignServerRelationId, true},
+ 	{"service", ForeignServerRelationId, true},
+ 	{"user", UserMappingRelationId, true},
+ 	{"password", UserMappingRelationId, true},
+ 	{"connect_timeout", ForeignServerRelationId, true},
+ 	{"dbname", ForeignServerRelationId, true},
+ 	{"host", ForeignServerRelationId, true},
+ 	{"hostaddr", ForeignServerRelationId, true},
+ 	{"port", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"client_encoding", ForeignServerRelationId, true},
+ #endif
+ 	{"tty", ForeignServerRelationId, true},
+ 	{"options", ForeignServerRelationId, true},
+ 	{"application_name", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"fallback_application_name", ForeignServerRelationId, true},
+ #endif
+ 	{"keepalives", ForeignServerRelationId, true},
+ 	{"keepalives_idle", ForeignServerRelationId, true},
+ 	{"keepalives_interval", ForeignServerRelationId, true},
+ 	{"keepalives_count", ForeignServerRelationId, true},
+ 	{"requiressl", ForeignServerRelationId, true},
+ 	{"sslcompression", ForeignServerRelationId, true},
+ 	{"sslmode", ForeignServerRelationId, true},
+ 	{"sslcert", ForeignServerRelationId, true},
+ 	{"sslkey", ForeignServerRelationId, true},
+ 	{"sslrootcert", ForeignServerRelationId, true},
+ 	{"sslcrl", ForeignServerRelationId, true},
+ 	{"requirepeer", ForeignServerRelationId, true},
+ 	{"krbsrvname", ForeignServerRelationId, true},
+ 	{"gsslib", ForeignServerRelationId, true},
+ #ifdef NOT_USED
+ 	{"replication", ForeignServerRelationId, true},
+ #endif
+ 
+ 	/*
+ 	 * Options for translation of object names.
+ 	 */
+ 	{"nspname", ForeignTableRelationId, false},
+ 	{"relname", ForeignTableRelationId, false},
+ 	{"colname", AttributeRelationId, false},
+ 
+ 	/*
+ 	 * Options for cursor behavior.
+ 	 * These options can be overridden by finer-grained objects.
+ 	 */
+ 	{"fetch_count", ForeignTableRelationId, false},
+ 	{"fetch_count", ForeignServerRelationId, false},
+ 
+ 	/* Terminating entry --- MUST BE LAST */
+ 	{NULL, InvalidOid, false}
+ };
+ 
+ /*
+  * Helper functions
+  */
+ static bool is_valid_option(const char *optname, Oid context);
+ 
+ /*
+  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+  * USER MAPPING or FOREIGN TABLE that uses pgsql_fdw.
+  *
+  * Raise an ERROR if the option or its value is considered invalid.
+  */
+ Datum
+ pgsql_fdw_validator(PG_FUNCTION_ARGS)
+ {
+ 	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+ 	Oid			catalog = PG_GETARG_OID(1);
+ 	ListCell   *cell;
+ 
+ 	/*
+ 	 * Check that only options supported by pgsql_fdw, and allowed for the
+ 	 * current object type, are given.
+ 	 */
+ 	foreach(cell, options_list)
+ 	{
+ 		DefElem    *def = (DefElem *) lfirst(cell);
+ 
+ 		if (!is_valid_option(def->defname, catalog))
+ 		{
+ 			PgsqlFdwOption *opt;
+ 			StringInfoData buf;
+ 
+ 			/*
+ 			 * Unknown option specified, complain about it. Provide a hint
+ 			 * with list of valid options for the object.
+ 			 */
+ 			initStringInfo(&buf);
+ 			for (opt = valid_options; opt->optname; opt++)
+ 			{
+ 				if (catalog == opt->optcontext)
+ 					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+ 									 opt->optname);
+ 			}
+ 
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+ 					 errmsg("invalid option \"%s\"", def->defname),
+ 					 errhint("Valid options in this context are: %s",
+ 							 buf.data)));
+ 		}
+ 
+ 		/* fetch_count be positive digit number. */
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 		{
+ 			long value;
+ 			char *p = NULL;
+ 
+ 			value = strtol(defGetString(def), &p, 10);
+ 			if (*p != '\0' || value < 1)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FDW_INVALID_ATTRIBUTE_VALUE),
+ 						 errmsg("invalid value for %s: \"%s\"",
+ 								def->defname, defGetString(def))));
+ 		}
+ 	}
+ 
+ 	/*
+ 	 * We don't care option-specific limitation here; they will be validated at
+ 	 * the execution time.
+ 	 */
+ 
+ 	PG_RETURN_VOID();
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid pgsql_fdw options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_valid_option(const char *optname, Oid context)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (context == opt->optcontext && strcmp(opt->optname, optname) == 0)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Check whether the given option is one of the valid libpq options.
+  * context is the Oid of the catalog holding the object the option is for.
+  */
+ static bool
+ is_libpq_option(const char *optname)
+ {
+ 	PgsqlFdwOption *opt;
+ 
+ 	for (opt = valid_options; opt->optname; opt++)
+ 	{
+ 		if (strcmp(opt->optname, optname) == 0 && opt->is_libpq_opt)
+ 			return true;
+ 	}
+ 	return false;
+ }
+ 
+ /*
+  * Generate key-value arrays which includes only libpq options from the list
+  * which contains any kind of options.
+  */
+ int
+ ExtractConnectionOptions(List *defelems, const char **keywords, const char **values)
+ {
+ 	ListCell *lc;
+ 	int i;
+ 
+ 	i = 0;
+ 	foreach(lc, defelems)
+ 	{
+ 		DefElem *d = (DefElem *) lfirst(lc);
+ 		if (is_libpq_option(d->defname))
+ 		{
+ 			keywords[i] = d->defname;
+ 			values[i] = defGetString(d);
+ 			i++;
+ 		}
+ 	}
+ 	return i;
+ }
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index ...b0ea2b2 .
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
***************
*** 0 ****
--- 1,39 ----
+ /* contrib/pgsql_fdw/pgsql_fdw--1.0.sql */
+ 
+ -- complain if script is sourced in psql, rather than via CREATE EXTENSION
+ \echo Use "CREATE EXTENSION pgsql_fdw" to load this file. \quit
+ 
+ CREATE FUNCTION pgsql_fdw_handler()
+ RETURNS fdw_handler
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_validator(text[], oid)
+ RETURNS void
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FOREIGN DATA WRAPPER pgsql_fdw
+   HANDLER pgsql_fdw_handler
+   VALIDATOR pgsql_fdw_validator;
+ 
+ /* connection management functions and view */
+ CREATE FUNCTION pgsql_fdw_get_connections(out srvid oid, out usesysid oid)
+ RETURNS SETOF record
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE FUNCTION pgsql_fdw_disconnect(oid, oid)
+ RETURNS text
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C STRICT;
+ 
+ CREATE VIEW pgsql_fdw_connections AS
+ SELECT c.srvid srvid,
+        s.srvname srvname,
+        c.usesysid usesysid,
+        pg_get_userbyid(c.usesysid) usename
+   FROM pgsql_fdw_get_connections() c
+            JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
+ GRANT SELECT ON pgsql_fdw_connections TO public;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index ...df7f407 .
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 0 ****
--- 1,891 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.c
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.c
+  *
+  *-------------------------------------------------------------------------
+  */
+ #include "postgres.h"
+ #include "fmgr.h"
+ 
+ #include "catalog/pg_foreign_server.h"
+ #include "catalog/pg_foreign_table.h"
+ #include "commands/defrem.h"
+ #include "commands/explain.h"
+ #include "foreign/fdwapi.h"
+ #include "funcapi.h"
+ #include "miscadmin.h"
+ #include "nodes/nodeFuncs.h"
+ #include "optimizer/cost.h"
+ #include "optimizer/pathnode.h"
+ #include "optimizer/planmain.h"
+ #include "optimizer/restrictinfo.h"
+ #include "utils/lsyscache.h"
+ #include "utils/memutils.h"
+ #include "utils/rel.h"
+ 
+ #include "pgsql_fdw.h"
+ #include "connection.h"
+ 
+ PG_MODULE_MAGIC;
+ 
+ /*
+  * Default fetch count for cursor.  This can be overridden by fetch_count FDW
+  * option.
+  */
+ #define DEFAULT_FETCH_COUNT			10000
+ 
+ /*
+  * Cost to establish a connection.
+  * XXX: should be configurable per server?
+  */
+ #define CONNECTION_COSTS			100.0
+ 
+ /*
+  * Cost to transfer 1 byte from remote server.
+  * XXX: should be configurable per server?
+  */
+ #define TRANSFER_COSTS_PER_BYTE		0.001
+ 
+ /*
+  * Cursors which are used together in a local query require different name, so
+  * we use simple incremental name for that purpose.  We don't care wrap around
+  * of cursor_id because it's hard to imagine that 2^32 cursors are used in a
+  * query.
+  */
+ #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
+ static uint32 cursor_id = 0;
+ 
+ /*
+  * Index of FDW-private information stored in fdw_private list.
+  *
+  * We store various information in ForeignScan.fdw_private to pass them beyond
+  * the boundary between planner and executor.  Finally FdwPlan using cursor
+  * would hold items below:
+  *
+  * 1) plain SELECT statement
+  * 2) SQL statement used to declare cursor
+  * 3) SQL statement used to fetch rows from cursor
+  * 5) SQL statement used to reset cursor
+  * 5) SQL statement used to close cursor
+  *
+  * These items are indexed with the enum FdwPrivateIndex, so an item
+  * can be accessed directly via list_nth().  For example of FETCH
+  * statement:
+  *      list_nth(fdw_private, FdwPrivateFetchSql)
+  */
+ enum FdwPrivateIndex {
+ 	/* SQL statements */
+ 	FdwPrivateSelectSql,
+ 	FdwPrivateDeclareSql,
+ 	FdwPrivateFetchSql,
+ 	FdwPrivateResetSql,
+ 	FdwPrivateCloseSql,
+ 
+ 	/* # of elements stored in the list fdw_private */
+ 	FdwPrivateNum,
+ };
+ 
+ /*
+  * Describes an execution state of a foreign scan against a foreign table
+  * using pgsql_fdw.
+  */
+ typedef struct PgsqlFdwExecutionState
+ {
+ 	MemoryContext scan_cxt;		/* context for per-scan lifespan data */
+ 
+ 	List	   *fdw_private;	/* FDW-private information */
+ 	PGconn	   *conn;			/* connection for the scan */
+ 
+ 	Oid		   *param_types;	/* type array of external parameter */
+ 	const char **param_values;	/* value array of external parameter */
+ 
+ 	int			attnum;			/* # of non-dropped attribute */
+ 	char	  **col_values;		/* column value buffer */
+ 	AttInMetadata *attinmeta;	/* attribute metadata */
+ 
+ 	Tuplestorestate *tuples;	/* result of the scan */
+ } PgsqlFdwExecutionState;
+ 
+ /*
+  * SQL functions
+  */
+ extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ 
+ /*
+  * FDW callback routines
+  */
+ static void pgsqlGetForeignRelSize(PlannerInfo *root,
+ 								   RelOptInfo *baserel,
+ 								   Oid foreigntableid);
+ static void pgsqlGetForeignPaths(PlannerInfo *root,
+ 								 RelOptInfo *baserel,
+ 								 Oid foreigntableid);
+ static ForeignScan *pgsqlGetForeignPlan(PlannerInfo *root,
+ 										RelOptInfo *baserel,
+ 										Oid foreigntableid,
+ 										ForeignPath *best_path,
+ 										List *tlist,
+ 										List *scan_clauses);
+ static void pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es);
+ static void pgsqlBeginForeignScan(ForeignScanState *node, int eflags);
+ static TupleTableSlot *pgsqlIterateForeignScan(ForeignScanState *node);
+ static void pgsqlReScanForeignScan(ForeignScanState *node);
+ static void pgsqlEndForeignScan(ForeignScanState *node);
+ 
+ /*
+  * Helper functions
+  */
+ static void adjust_costs(double rows, int width,
+ 						 Cost *startup_cost, Cost *total_cost);
+ static void execute_query(ForeignScanState *node);
+ static PGresult *fetch_result(ForeignScanState *node);
+ static void store_result(ForeignScanState *node, PGresult *res);
+ 
+ /* Exported functions, but not written in pgsql_fdw.h. */
+ void _PG_init(void);
+ void _PG_fini(void);
+ 
+ /*
+  * Module-specific initialization.
+  */
+ void
+ _PG_init(void)
+ {
+ }
+ 
+ /*
+  * Module-specific clean up.
+  */
+ void
+ _PG_fini(void)
+ {
+ }
+ 
+ /*
+  * The content of FdwRoutine of pgsql_fdw is never changed, so we use one
+  * static object for all scan.
+  */
+ static FdwRoutine fdwroutine = {
+ 
+ 	/* Node type */
+ 	T_FdwRoutine,
+ 
+ 	/* Required handler functions. */
+ 	pgsqlGetForeignRelSize,
+ 	pgsqlGetForeignPaths,
+ 	pgsqlGetForeignPlan,
+ 	pgsqlExplainForeignScan,
+ 	pgsqlBeginForeignScan,
+ 	pgsqlIterateForeignScan,
+ 	pgsqlReScanForeignScan,
+ 	pgsqlEndForeignScan,
+ 
+ 	/* Optional handler functions. */
+ };
+ 
+ /*
+  * Foreign-data wrapper handler function: return a struct with pointers
+  * to my callback routines.
+  */
+ Datum
+ pgsql_fdw_handler(PG_FUNCTION_ARGS)
+ {
+ 	PG_RETURN_POINTER(&fdwroutine);
+ }
+ 
+ /*
+  * pgsqlGetForeignRelSize
+  *		Estimate # of rows and width of the result of the scan
+  */
+ static void
+ pgsqlGetForeignRelSize(PlannerInfo *root,
+ 					   RelOptInfo *baserel,
+ 					   Oid foreigntableid)
+ {
+ 	/* Estimate # of rows by calling set_baserel_size_estimates(). */
+ 	set_baserel_size_estimates(root, baserel);
+ }
+ 
+ /*
+  * pgsqlGetForeignPaths
+  *		Create possible scan paths for a scan on the foreign table
+  */
+ static void
+ pgsqlGetForeignPaths(PlannerInfo *root,
+ 					 RelOptInfo *baserel,
+ 					 Oid foreigntableid)
+ {
+ 	Path		   *seqscan;
+ 	ForeignPath	   *path;
+ 	Cost			startup_cost;
+ 	Cost			total_cost;
+ 
+ 	/*
+ 	 * First, we estimate rough cost with assuming sequential scan is
+ 	 * performed on remote side.  Those  cost estimation should be modified
+ 	 * to respect cost of establishing connection and transferring data.
+ 	 * This design might cause overestimate, but it seems better than
+ 	 * underestimate.
+ 	 */
+ 	seqscan = create_seqscan_path(root, baserel);
+ 	cost_seqscan(seqscan, root, baserel);
+ 	startup_cost = seqscan->startup_cost;
+ 	total_cost = seqscan->total_cost;
+ 	adjust_costs(baserel->rows, baserel->width, &startup_cost, &total_cost);
+ 
+ 	/*
+ 	 * Create simplest ForeignScan path node and add it to baserel.  This path
+ 	 * corresponds to SeqScan path of regular tables.
+ 	 */
+ 	path = create_foreignscan_path(root, baserel,
+ 								   baserel->rows,
+ 								   startup_cost,
+ 								   total_cost,
+ 								   NIL,				/* no pathkeys */
+ 								   NULL,			/* no outer rel either */
+ 								   NIL,				/* no param clause */
+ 								   NIL);			/* no FDW private */
+ 	add_path(baserel, (Path *) path); 
+ 
+ 	/*
+ 	 * XXX We can consider sorted path or parameterized path here if we know
+ 	 * that foreign table is indexed on remote end.  For this purpose, we
+ 	 * might have to support FOREIGN INDEX to represent possible sets of sort
+ 	 * keys and/or filtering.
+ 	 */
+ }
+ 
+ /*
+  * pgsqlGetForeignPlan
+  *		Create ForeignScan plan node which implements selected best path
+  */
+ static ForeignScan *
+ pgsqlGetForeignPlan(PlannerInfo *root,
+ 					RelOptInfo *baserel,
+ 					Oid foreigntableid,
+ 					ForeignPath *best_path,
+ 					List *tlist,
+ 					List *scan_clauses)
+ {
+ 	Index			scan_relid = baserel->relid;
+ 	List		   *fdw_private = NIL;
+ 	ListCell	   *lc;
+ 	char			name[128];	/* must be larger than format + 10 */
+ 	StringInfoData	cursor;
+ 	DefElem		   *def;
+ 	int				fetch_count = DEFAULT_FETCH_COUNT;
+ 	char		   *sql;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 
+ 	/*
+ 	 * We have no native ability to evaluate restriction clauses, so we just
+ 	 * put all the scan_clauses into the plan node's qual list for the
+ 	 * executor to check.  So all we have to do here is strip RestrictInfo
+ 	 * nodes from the clauses and ignore pseudoconstants (which will be
+ 	 * handled elsewhere).
+ 	 */
+ 	scan_clauses = extract_actual_clauses(scan_clauses, false);
+ 
+ 	/*
+ 	 * Use specified fetch_count instead of default value, if any.  Foreign
+ 	 * table option overrides server option.
+ 	 */
+ 	table = GetForeignTable(foreigntableid);
+ 	foreach(lc, table->options)
+ 	{
+ 		def = (DefElem *) lfirst(lc);
+ 		if (strcmp(def->defname, "fetch_count") == 0)
+ 			break;
+  
+ 	}
+ 	if (lc == NULL)
+ 	{
+ 		server = GetForeignServer(table->serverid);
+ 		foreach(lc, server->options)
+ 		{
+ 			def = (DefElem *) lfirst(lc);
+ 			if (strcmp(def->defname, "fetch_count") == 0)
+ 				break;
+ 	 
+ 		}
+ 	}
+ 	if (lc != NULL)
+ 		fetch_count = strtol(defGetString(def), NULL, 10);
+ 	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
+ 
+ 	/*
+ 	 * Construct simple remote query which has no WHERE clause.
+ 	 */
+ 	sql = deparseSimpleSql(foreigntableid, root, baserel, table);
+ 	fdw_private = lappend(fdw_private, makeString(sql));
+ 
+ 	/* Construct cursor name from sequential value */
+ 	sprintf(name, CURSOR_NAME_FORMAT, cursor_id++);
+ 
+ 	/* Construct statement to declare cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "DECLARE %s SCROLL CURSOR FOR %s", name, sql);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to fetch rows from cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "FETCH %d FROM %s", fetch_count, name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to reset cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "MOVE ABSOLUTE 0 FROM %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Construct statement to close cursor */
+ 	initStringInfo(&cursor);
+ 	appendStringInfo(&cursor, "CLOSE %s", name);
+ 	fdw_private = lappend(fdw_private, makeString(cursor.data));
+ 
+ 	/* Create the ForeignScan node with fdw_private of selected path. */
+ 	return make_foreignscan(tlist,
+ 							scan_clauses,
+ 							scan_relid,
+ 							NIL,
+ 							fdw_private);
+ }
+ 
+ /*
+  * pgsqlExplainForeignScan
+  *		Produce extra output for EXPLAIN
+  */
+ static void
+ pgsqlExplainForeignScan(ForeignScanState *node, ExplainState *es)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 
+ 	/* CURSOR declaration is shown in only VERBOSE mode. */
+ 	fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 	if (es->verbose)
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 	else
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateSelectSql));
+ 	ExplainPropertyText("Remote SQL", sql, es);
+ }
+ 
+ /*
+  * pgsqlBeginForeignScan
+  *		Initiate access to a foreign PostgreSQL table.
+  */
+ static void
+ pgsqlBeginForeignScan(ForeignScanState *node, int eflags)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	PGconn		   *conn;
+ 	Oid				relid;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	UserMapping	   *user;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 
+ 	/*
+ 	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+ 	 */
+ 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+ 		return;
+ 
+ 	/*
+ 	 * Save state in node->fdw_state.
+ 	 */
+ 	festate = (PgsqlFdwExecutionState *) palloc(sizeof(PgsqlFdwExecutionState));
+ 	festate->fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 
+ 	/*
+ 	 * Create context for per-scan tuplestore under per-query context.
+ 	 */
+ 	festate->scan_cxt = AllocSetContextCreate(node->ss.ps.state->es_query_cxt,
+ 											  "pgsql_fdw",
+ 											  ALLOCSET_DEFAULT_MINSIZE,
+ 											  ALLOCSET_DEFAULT_INITSIZE,
+ 											  ALLOCSET_DEFAULT_MAXSIZE);
+ 
+ 	/*
+ 	 * Get connection to the foreign server.  Connection manager would
+ 	 * establish new connection if necessary.
+ 	 */
+ 	relid = RelationGetRelid(node->ss.ss_currentRelation);
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	user = GetUserMapping(GetOuterUserId(), server->serverid);
+ 	conn = GetConnection(server, user, true);
+ 	festate->conn = conn;
+ 
+ 	/* Result will be filled in first Iterate call. */
+ 	festate->tuples = NULL;
+ 
+ 	/* Allocate buffers for column values. */
+ 	{
+ 		TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 		festate->col_values = palloc(sizeof(char *) * tupdesc->natts);
+ 		festate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ 	}
+ 
+ 	/* Allocate buffers for query parameters. */
+ 	{
+ 		ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 		int				numParams = params ? params->numParams : 0;
+ 
+ 		if (numParams > 0)
+ 		{
+ 			festate->param_types = palloc0(sizeof(Oid) * numParams);
+ 			festate->param_values = palloc0(sizeof(char *) * numParams);
+ 		}
+ 		else
+ 		{
+ 			festate->param_types = NULL;
+ 			festate->param_values = NULL;
+ 		}
+ 	}
+ 
+ 	/* Store FDW-specific state into ForeignScanState */
+ 	node->fdw_state = (void *) festate;
+ 
+ 	return;
+ }
+ 
+ /*
+  * pgsqlIterateForeignScan
+  *		Retrieve next row from the result set, or clear tuple slot to indicate
+  *		EOF.
+  *
+  *		Note that using per-query context when retrieving tuples from
+  *		tuplestore to ensure that returned tuples can survive until next
+  *		iteration because the tuple is released implicitly via ExecClearTuple.
+  *		Retrieving a tuple from tuplestore in CurrentMemoryContext (it's a
+  *		per-tuple context), ExecClearTuple will free dangling pointer.
+  */
+ static TupleTableSlot *
+ pgsqlIterateForeignScan(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	PGresult	   *res = NULL;
+ 	MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/*
+ 	 * If this is the first call after Begin, we need to execute remote query.
+ 	 * If the query needs cursor, we declare a cursor at first call and fetch
+ 	 * from it in later calls.
+ 	 */
+ 	if (festate->tuples == NULL)
+ 		execute_query(node);
+ 
+ 	/*
+ 	 * If enough tuples are left in tuplestore, just return next tuple from it.
+ 	 *
+ 	 * It is necessary to switch to per-scan context to make returned tuple
+ 	 * valid until next IterateForeignScan call, because it will be released
+ 	 * with ExecClearTuple then.  Otherwise, picked tuple is allocated in
+ 	 * per-tuple context, and double-free of that tuple might happen.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/*
+ 	 * Here we need to clear partial result and fetch next bunch of tuples from
+ 	 * from the cursor for the scan.  If the fetch returns no tuple, the scan
+ 	 * has reached the end.
+ 	 *
+ 	 * PGresult must be released before leaving this function.
+ 	 */
+ 	PG_TRY();
+ 	{
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * If we got more tuples from the server cursor, return next tuple from
+ 	 * tuplestore.
+ 	 */
+ 	MemoryContextSwitchTo(festate->scan_cxt);
+ 	if (tuplestore_gettupleslot(festate->tuples, true, false, slot))
+ 	{
+ 		MemoryContextSwitchTo(oldcontext);
+ 		return slot;
+ 	}
+ 	MemoryContextSwitchTo(oldcontext);
+ 
+ 	/* We don't have any result even in remote server cursor. */
+ 	ExecClearTuple(slot);
+ 	return slot;
+ }
+ 
+ /*
+  * pgsqlReScanForeignScan
+  *   - Restart this scan by resetting fetch location.
+  */
+ static void
+ pgsqlReScanForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results if any. */
+ 	tuplestore_clear(festate->tuples);
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Reset cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateResetSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not rewind cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * pgsqlEndForeignScan
+  *		Finish scanning foreign table and dispose objects used for this scan
+  */
+ static void
+ pgsqlEndForeignScan(ForeignScanState *node)
+ {
+ 	List	   *fdw_private;
+ 	char	   *sql;
+ 	PGconn	   *conn;
+ 	PGresult   *res = NULL;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+ 	if (festate == NULL)
+ 		return;
+ 
+ 	/* If we have not opened cursor yet, nothing to do. */
+ 	if (festate->tuples == NULL)
+ 		return;
+ 
+ 	/* Discard fetch results */
+ 	tuplestore_end(festate->tuples);
+ 	festate->tuples = NULL;
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/* Close cursor */
+ 		fdw_private = festate->fdw_private;
+ 		conn = festate->conn;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateCloseSql));
+ 		res = PQexec(conn, sql);
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not close cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	ReleaseConnection(festate->conn);
+ 
+ 	MemoryContextDelete(festate->scan_cxt);
+ 	festate->scan_cxt = NULL;
+ }
+ 
+ /*
+  * Adjust costs estimated on remote end with some overheads such as connection
+  * and data transfer.
+  */
+ static void
+ adjust_costs(double rows, int width, Cost *startup_cost, Cost *total_cost)
+ {
+ 	/*
+ 	 * TODO Selectivity of quals which are NOT pushed down should be also
+ 	 * considered.
+ 	 */
+ 
+ 	/* add cost to establish connection. */
+ 	*startup_cost += CONNECTION_COSTS;
+ 	*total_cost += CONNECTION_COSTS;
+ 
+ 	/* add cost to transfer result. */
+ 	*total_cost += TRANSFER_COSTS_PER_BYTE * width * rows;
+ 	*total_cost += cpu_tuple_cost * rows;
+ }
+ 
+ /*
+  * Execute remote query with current parameters.
+  */
+ static void
+ execute_query(ForeignScanState *node)
+ {
+ 	List		   *fdw_private;
+ 	PgsqlFdwExecutionState *festate;
+ 	ParamListInfo	params = node->ss.ps.state->es_param_list_info;
+ 	int				numParams = params ? params->numParams : 0;
+ 	Oid			   *types = NULL;
+ 	const char	  **values = NULL;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	types = festate->param_types;
+ 	values = festate->param_values;
+ 
+ 	/*
+ 	 * Construct parameter array in text format.  We don't release memory for
+ 	 * the arrays explicitly, because the memory usage would not be very large,
+ 	 * and anyway they will be released in context cleanup.
+ 	 */
+ 	if (numParams > 0)
+ 	{
+ 		int i;
+ 
+ 		for (i = 0; i < numParams; i++)
+ 		{
+ 			types[i] = params->params[i].ptype;
+ 			if (params->params[i].isnull)
+ 				values[i] = NULL;
+ 			else
+ 			{
+ 				Oid			out_func_oid;	
+ 				bool		isvarlena;
+ 				FmgrInfo	func;
+ 
+ 				getTypeOutputInfo(types[i], &out_func_oid, &isvarlena);
+ 				fmgr_info(out_func_oid, &func);
+ 				values[i] = OutputFunctionCall(&func, params->params[i].value);
+ 			}
+ 		}
+ 	}
+ 
+ 	/* PGresult must be released before leaving this function. */
+ 	PG_TRY();
+ 	{
+ 		/*
+ 		 * Execute remote query with parameters.
+ 		 */
+ 		conn = festate->conn;
+ 		fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
+ 		sql = strVal(list_nth(fdw_private, FdwPrivateDeclareSql));
+ 		res = PQexecParams(conn, sql, numParams, types, values, NULL, NULL, 0);
+ 
+ 		/*
+ 		 * If the query has failed, reporting details is enough here.
+ 		 * Connection(s) which are used by this query (at least used by
+ 		 * pgsql_fdw) will be cleaned up by the foreign connection manager.
+ 		 */
+ 		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("could not declare cursor"),
+ 					 errdetail("%s", PQerrorMessage(conn)),
+ 					 errhint("%s", sql)));
+ 		}
+ 
+ 		/* Discard result of DECLARE statement. */
+ 		PQclear(res);
+ 		res = NULL;
+ 
+ 		/* Fetch first bunch of the result and store them into tuplestore. */
+ 		res = fetch_result(node);
+ 		store_result(node, res);
+ 		PQclear(res);
+ 		res = NULL;
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ }
+ 
+ /*
+  * Fetch next partial result from remote server.
+  *
+  * Once this function has returned result records as PGresult, caller is
+  * responsible to release it, so caller should put codes which might throw
+  * exception in PG_TRY block.  When an exception has been caught, release
+  * PGresult and re-throw the exception in PG_CATCH block.
+  */
+ static PGresult *
+ fetch_result(ForeignScanState *node)
+ {
+ 	PgsqlFdwExecutionState *festate;
+ 	List		   *fdw_private;
+ 	char		   *sql;
+ 	PGconn		   *conn;
+ 	PGresult	   *res;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 
+ 	/* Retrieve information for fetching result. */
+ 	fdw_private = festate->fdw_private;
+ 	sql = strVal(list_nth(fdw_private, FdwPrivateFetchSql));
+ 	conn = festate->conn;
+ 
+ 	/*
+ 	 * Fetch result from remote server.  In error case, we must release
+ 	 * PGresult in this function to avoid memory leak because caller can't
+ 	 * get the reference.
+ 	 */
+ 	res = PQexec(conn, sql);
+ 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 	{
+ 		PQclear(res);
+ 		ereport(ERROR,
+ 				(errmsg("could not fetch rows from foreign server"),
+ 				 errdetail("%s", PQerrorMessage(conn)),
+ 				 errhint("%s", sql)));
+ 	}
+ 
+ 	return res;
+ }
+ 
+ /*
+  * Create tuples from PGresult and store them into tuplestore.
+  *
+  * Caller must use PG_TRY block to catch exception and release PGresult
+  * surely.
+  */
+ static void
+ store_result(ForeignScanState *node, PGresult *res)
+ {
+ 	int					rows;
+ 	int					row;
+ 	int					i;
+ 	int					nfields;
+ 	int					attnum;		/* number of non-dropped columns */
+ 	Form_pg_attribute  *attrs;
+ 	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+ 	TupleDesc	tupdesc = slot->tts_tupleDescriptor;
+ 	PgsqlFdwExecutionState *festate;
+ 
+ 	festate = (PgsqlFdwExecutionState *) node->fdw_state;
+ 	rows = PQntuples(res);
+ 	nfields = PQnfields(res);
+ 	attrs = tupdesc->attrs;
+ 
+ 	/* First, ensure that the tuplestore is empty. */
+ 	if (festate->tuples == NULL)
+ 	{
+ 		MemoryContext	oldcontext = CurrentMemoryContext;
+ 
+ 		/*
+ 		 * Create tuplestore to store result of the query in per-query context.
+ 		 * Note that we use this memory context to avoid memory leak in error
+ 		 * cases.
+ 		 */
+ 		MemoryContextSwitchTo(festate->scan_cxt);
+ 		festate->tuples = tuplestore_begin_heap(false, false, work_mem);
+ 		MemoryContextSwitchTo(oldcontext);
+ 	}
+ 	else
+ 	{
+ 		/* We already have tuplestore, just need to clear contents of it. */
+ 		tuplestore_clear(festate->tuples);
+ 	}
+ 
+ 	/* count non-dropped columns */
+ 	for (attnum = 0, i = 0; i < tupdesc->natts; i++)
+ 		if (!attrs[i]->attisdropped)
+ 			attnum++;
+ 
+ 	/* check result and tuple descriptor have the same number of columns */
+ 	if (attnum > 0 && attnum != nfields)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_DATATYPE_MISMATCH),
+ 				 errmsg("remote query result rowtype does not match "
+ 						"the specified FROM clause rowtype"),
+ 				 errdetail("expected %d, actual %d", attnum, nfields)));
+ 
+ 	/* put a tuples into the slot */
+ 	for (row = 0; row < rows; row++)
+ 	{
+ 		int			j;
+ 		HeapTuple	tuple;
+ 
+ 		for (i = 0, j = 0; i < tupdesc->natts; i++)
+ 		{
+ 			/* skip dropped columns. */
+ 			if (attrs[i]->attisdropped)
+ 			{
+ 				festate->col_values[i] = NULL;
+ 				continue;
+ 			}
+ 
+ 			if (PQgetisnull(res, row, j))
+ 				festate->col_values[i] = NULL;
+ 			else
+ 				festate->col_values[i] = PQgetvalue(res, row, j);
+ 			j++;
+ 		}
+ 
+ 		/*
+ 		 * Build the tuple and put it into the slot.
+ 		 * We don't have to free the tuple explicitly because it's been
+ 		 * allocated in the per-tuple context.
+ 		 */
+ 		tuple = BuildTupleFromCStrings(festate->attinmeta, festate->col_values);
+ 		tuplestore_puttuple(festate->tuples, tuple);
+ 	}
+ 
+ 	tuplestore_donestoring(festate->tuples);
+ }
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.control b/contrib/pgsql_fdw/pgsql_fdw.control
index ...0a9c8f4 .
*** a/contrib/pgsql_fdw/pgsql_fdw.control
--- b/contrib/pgsql_fdw/pgsql_fdw.control
***************
*** 0 ****
--- 1,5 ----
+ # pgsql_fdw extension
+ comment = 'foreign-data wrapper for remote PostgreSQL servers'
+ default_version = '1.0'
+ module_pathname = '$libdir/pgsql_fdw'
+ relocatable = true
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index ...6eb99d5 .
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 0 ****
--- 1,32 ----
+ /*-------------------------------------------------------------------------
+  *
+  * pgsql_fdw.h
+  *		  foreign-data wrapper for remote PostgreSQL servers.
+  *
+  * Copyright (c) 2012, PostgreSQL Global Development Group
+  *
+  * IDENTIFICATION
+  *		  contrib/pgsql_fdw/pgsql_fdw.h
+  *
+  *-------------------------------------------------------------------------
+  */
+ 
+ #ifndef PGSQL_FDW_H
+ #define PGSQL_FDW_H
+ 
+ #include "postgres.h"
+ #include "foreign/foreign.h"
+ #include "nodes/relation.h"
+ 
+ /* in option.c */
+ int ExtractConnectionOptions(List *defelems,
+ 							 const char **keywords,
+ 							 const char **values);
+ 
+ /* in deparse.c */
+ char *deparseSimpleSql(Oid relid,
+ 					   PlannerInfo *root,
+ 					   RelOptInfo *baserel,
+ 					   ForeignTable *table);
+ 
+ #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index ...b3fac96 .
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
***************
*** 0 ****
--- 1,248 ----
+ -- ===================================================================
+ -- create FDW objects
+ -- ===================================================================
+ 
+ -- Clean up in case a prior regression run failed
+ 
+ -- Suppress NOTICE messages when roles don't exist
+ SET client_min_messages TO 'error';
+ 
+ DROP ROLE IF EXISTS pgsql_fdw_user;
+ 
+ RESET client_min_messages;
+ 
+ CREATE ROLE pgsql_fdw_user LOGIN SUPERUSER;
+ SET SESSION AUTHORIZATION 'pgsql_fdw_user';
+ 
+ CREATE EXTENSION pgsql_fdw;
+ 
+ CREATE SERVER loopback1 FOREIGN DATA WRAPPER pgsql_fdw;
+ CREATE SERVER loopback2 FOREIGN DATA WRAPPER pgsql_fdw
+   OPTIONS (dbname 'contrib_regression');
+ 
+ CREATE USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (user 'value', password 'value');
+ CREATE USER MAPPING FOR pgsql_fdw_user SERVER loopback2;
+ 
+ CREATE FOREIGN TABLE ft1 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft1 DROP COLUMN c0;
+ 
+ CREATE FOREIGN TABLE ft2 (
+ 	c0 int,
+ 	c1 int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10)
+ ) SERVER loopback2;
+ ALTER FOREIGN TABLE ft2 DROP COLUMN c0;
+ 
+ -- ===================================================================
+ -- create objects used through FDW
+ -- ===================================================================
+ CREATE SCHEMA "S 1";
+ CREATE TABLE "S 1"."T 1" (
+ 	"C 1" int NOT NULL,
+ 	c2 int NOT NULL,
+ 	c3 text,
+ 	c4 timestamptz,
+ 	c5 timestamp,
+ 	c6 varchar(10),
+ 	c7 char(10),
+ 	CONSTRAINT t1_pkey PRIMARY KEY ("C 1")
+ );
+ CREATE TABLE "S 1"."T 2" (
+ 	c1 int NOT NULL,
+ 	c2 text,
+ 	CONSTRAINT t2_pkey PRIMARY KEY (c1)
+ );
+ 
+ BEGIN;
+ TRUNCATE "S 1"."T 1";
+ INSERT INTO "S 1"."T 1"
+ 	SELECT id,
+ 	       id % 10,
+ 	       to_char(id, 'FM00000'),
+ 	       '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
+ 	       '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
+ 	       id % 10,
+ 	       id % 10
+ 	FROM generate_series(1, 1000) id;
+ TRUNCATE "S 1"."T 2";
+ INSERT INTO "S 1"."T 2"
+ 	SELECT id,
+ 	       'AAA' || to_char(id, 'FM000')
+ 	FROM generate_series(1, 100) id;
+ COMMIT;
+ 
+ -- ===================================================================
+ -- tests for pgsql_fdw_validator
+ -- ===================================================================
+ ALTER FOREIGN DATA WRAPPER pgsql_fdw OPTIONS (host 'value');    -- ERROR
+ -- requiressl, krbsrvname and gsslib are omitted because they depend on
+ -- configure option
+ ALTER SERVER loopback1 OPTIONS (
+ 	authtype 'value',
+ 	service 'value',
+ 	connect_timeout 'value',
+ 	dbname 'value',
+ 	host 'value',
+ 	hostaddr 'value',
+ 	port 'value',
+ 	--client_encoding 'value',
+ 	tty 'value',
+ 	options 'value',
+ 	application_name 'value',
+ 	--fallback_application_name 'value',
+ 	keepalives 'value',
+ 	keepalives_idle 'value',
+ 	keepalives_interval 'value',
+ 	-- requiressl 'value',
+ 	sslcompression 'value',
+ 	sslmode 'value',
+ 	sslcert 'value',
+ 	sslkey 'value',
+ 	sslrootcert 'value',
+ 	sslcrl 'value'
+ 	--requirepeer 'value',
+ 	-- krbsrvname 'value',
+ 	-- gsslib 'value',
+ 	--replication 'value'
+ );
+ ALTER SERVER loopback1 OPTIONS (user 'value');                  -- ERROR
+ ALTER SERVER loopback2 OPTIONS (ADD fetch_count '2');
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (DROP user, DROP password);
+ ALTER USER MAPPING FOR public SERVER loopback1
+ 	OPTIONS (host 'value');                                     -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (nspname 'S 1', relname 'T 1');
+ ALTER FOREIGN TABLE ft2 OPTIONS (nspname 'S 1', relname 'T 1', fetch_count '100');
+ ALTER FOREIGN TABLE ft1 OPTIONS (invalid 'value');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count 'a');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '0');              -- ERROR
+ ALTER FOREIGN TABLE ft1 OPTIONS (fetch_count '-1');             -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (invalid 'value'); -- ERROR
+ ALTER FOREIGN TABLE ft1 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (colname 'C 1');
+ \dew+
+ \des+
+ \deu+
+ \det+
+ 
+ -- ===================================================================
+ -- simple queries
+ -- ===================================================================
+ -- single table, with/without alias
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- with WHERE clause
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
+ -- aggregate
+ SELECT COUNT(*) FROM ft1 t1;
+ -- join two tables
+ SELECT t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
+ -- subquery
+ SELECT * FROM ft1 t1 WHERE t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 <= 10) ORDER BY c1;
+ -- subquery+MAX
+ SELECT * FROM ft1 t1 WHERE t1.c3 = (SELECT MAX(c3) FROM ft2 t2) ORDER BY c1;
+ -- used in CTE
+ WITH t1 AS (SELECT * FROM ft1 WHERE c1 <= 10) SELECT t2.c1, t2.c2, t2.c3, t2.c4 FROM t1, ft2 t2 WHERE t1.c1 = t2.c1 ORDER BY t1.c1;
+ -- fixed values
+ SELECT 'fixed', NULL FROM ft1 t1 WHERE c1 = 1;
+ -- user-defined operator/function
+ CREATE FUNCTION pgsql_fdw_abs(int) RETURNS int AS $$
+ BEGIN
+ RETURN abs($1);
+ END
+ $$ LANGUAGE plpgsql IMMUTABLE;
+ CREATE OPERATOR === (
+     LEFTARG = int,
+     RIGHTARG = int,
+     PROCEDURE = int4eq,
+     COMMUTATOR = ===,
+     NEGATOR = !==
+ );
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = pgsql_fdw_abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ 
+ -- ===================================================================
+ -- parameterized queries
+ -- ===================================================================
+ -- simple join
+ PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
+ EXPLAIN (COSTS false) EXECUTE st1(1, 2);
+ EXECUTE st1(1, 1);
+ EXECUTE st1(101, 101);
+ -- subquery using stable function (can't be pushed down)
+ PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st2(10, 20);
+ EXECUTE st2(10, 20);
+ EXECUTE st1(101, 101);
+ -- subquery using immutable function (can be pushed down)
+ PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
+ EXPLAIN (COSTS false) EXECUTE st3(10, 20);
+ EXECUTE st3(10, 20);
+ EXECUTE st3(20, 30);
+ -- custom plan should be chosen
+ PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ EXPLAIN (COSTS false) EXECUTE st4(1);
+ -- cleanup
+ DEALLOCATE st1;
+ DEALLOCATE st2;
+ DEALLOCATE st3;
+ DEALLOCATE st4;
+ 
+ -- ===================================================================
+ -- connection management
+ -- ===================================================================
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_get_connections();
+ SELECT srvname, usename FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- subtransaction
+ -- ===================================================================
+ BEGIN;
+ DECLARE c CURSOR FOR SELECT * FROM ft1 ORDER BY c1;
+ FETCH c;
+ SAVEPOINT s;
+ ERROR OUT;          -- ERROR
+ ROLLBACK TO s;
+ SELECT srvname FROM pgsql_fdw_connections;
+ FETCH c;
+ COMMIT;
+ SELECT srvname FROM pgsql_fdw_connections;
+ ERROR OUT;          -- ERROR
+ SELECT srvname FROM pgsql_fdw_connections;
+ 
+ -- ===================================================================
+ -- cleanup
+ -- ===================================================================
+ DROP OPERATOR === (int, int) CASCADE;
+ DROP OPERATOR !== (int, int) CASCADE;
+ DROP FUNCTION pgsql_fdw_abs(int);
+ DROP SCHEMA "S 1" CASCADE;
+ DROP EXTENSION pgsql_fdw CASCADE;
+ \c
+ DROP ROLE pgsql_fdw_user;
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d4da4ee..32056d1 100644
*** a/doc/src/sgml/contrib.sgml
--- b/doc/src/sgml/contrib.sgml
*************** CREATE EXTENSION <replaceable>module_nam
*** 117,122 ****
--- 117,123 ----
   &pgcrypto;
   &pgfreespacemap;
   &pgrowlocks;
+  &pgsql-fdw;
   &pgstandby;
   &pgstatstatements;
   &pgstattuple;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b5d3c6d..de686ee 100644
*** a/doc/src/sgml/filelist.sgml
--- b/doc/src/sgml/filelist.sgml
***************
*** 125,130 ****
--- 125,131 ----
  <!ENTITY pgcrypto        SYSTEM "pgcrypto.sgml">
  <!ENTITY pgfreespacemap  SYSTEM "pgfreespacemap.sgml">
  <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+ <!ENTITY pgsql-fdw       SYSTEM "pgsql-fdw.sgml">
  <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
  <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
  <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index ...eb69f01 .
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
***************
*** 0 ****
--- 1,265 ----
+ <!-- doc/src/sgml/pgsql-fdw.sgml -->
+ 
+ <sect1 id="pgsql-fdw" xreflabel="pgsql_fdw">
+  <title>pgsql_fdw</title>
+ 
+  <indexterm zone="pgsql-fdw">
+   <primary>pgsql_fdw</primary>
+  </indexterm>
+ 
+  <para>
+   The <filename>pgsql_fdw</filename> module provides a foreign-data wrapper for
+   external <productname>PostgreSQL</productname> servers.
+   With this module, users can access data stored in external
+   <productname>PostgreSQL</productname> via plain SQL statements.
+  </para>
+ 
+  <para>
+   Note that default wrapper <literal>pgsql_fdw</literal> is created
+   automatically during <command>CREATE EXTENSION</command> command for
+   <application>pgsql_fdw</application>.
+  </para>
+ 
+  <sect2>
+   <title>FDW Options of pgsql_fdw</title>
+ 
+   <sect3>
+    <title>Connection Options</title>
+    <para>
+     A foreign server and user mapping created using this wrapper can have
+     <application>libpq</> connection options, expect below:
+ 
+     <itemizedlist>
+      <listitem><para>client_encoding</para></listitem>
+      <listitem><para>fallback_application_name</para></listitem>
+      <listitem><para>replication</para></listitem>
+     </itemizedlist>
+ 
+     For details of <application>libpq</> connection options, see
+     <xref linkend="libpq-connect">.
+    </para>
+ 
+    <para>
+     <literal>user</literal> and <literal>password</literal> can be
+     specified on user mappings, and others can be specified on foreign servers.
+    </para>
+   </sect3>
+ 
+   <sect3>
+    <title>Object Name Options</title>
+    <para>
+     Foreign tables which were created using this wrapper, or its columns can
+     have object name options.  These options can be used to specify the names
+     used in SQL statement sent to remote <productname>PostgreSQL</productname>
+     server.  These options are useful when a remote object has different name
+     from corresponding local one.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>nspname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        namespace (schema) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.nspname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>relname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a foreign table, is used as a
+        relation (table) reference in the SQL statement.  If this options is
+        omitted, <literal>pg_class.relname</literal> of the foreign table is
+        used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+     <varlistentry>
+      <term><literal>colname</literal></term>
+      <listitem>
+       <para>
+        This option, which can be specified on a column of a foreign table, is
+        used as a column (attribute) reference in the SQL statement.  If this
+        option is omitted, <literal>pg_attribute.attname</literal> of the column
+        of the foreign table is used.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+   <sect3>
+    <title>Cursor Options</title>
+    <para>
+     The <application>pgsql_fdw</application> always uses cursor to retrieve the
+     result from external server.  Users can control the behavior of cursor by
+     setting cursor options to foreign table or foreign server.  If an option
+     is set to both objects, finer-grained setting is used.  In other words,
+     foreign table's setting overrides foreign server's setting.
+    </para>
+ 
+    <variablelist>
+ 
+     <varlistentry>
+      <term><literal>fetch_count</literal></term>
+      <listitem>
+       <para>
+        This option specifies the number of rows to be fetched at a time.
+        This option accepts only integer value larger than zero.  The default
+        setting is 10000.
+       </para>
+      </listitem>
+     </varlistentry>
+ 
+    </variablelist>
+ 
+   </sect3>
+ 
+  </sect2>
+ 
+  <sect2>
+   <title>Connection Management</title>
+ 
+   <para>
+    The <application>pgsql_fdw</application> establishes a connection to a
+    foreign server in the beginning of the first query which uses a foreign
+    table associated to the foreign server, and reuses the connection following
+    queries and even in following foreign scans in same query.
+ 
+    You can see the list of active connections via
+    <structname>pgsql_fdw_connections</structname> view.  It shows pair of oid
+    and name of server and local role for each active connections established by
+    <application>pgsql_fdw</application>.  For security reason, only superuser
+    can see other role's connections.
+   </para>
+ 
+   <para>
+    Established connections are kept alive until local role changes or the
+    current transaction aborts or user requests so.
+   </para>
+ 
+   <para>
+    If role has been changed, active connections established as old local role
+    is kept alive but never be reused until local role has restored to original
+    role.  This kind of situation happens with <command>SET ROLE</command> and
+    <command>SET SESSION AUTHORIZATION</command>.
+   </para>
+ 
+   <para>
+    If current transaction aborts by error or user request, all active
+    connections are disconnected automatically.  This behavior avoids possible
+    connection leaks on error.
+   </para>
+ 
+   <para>
+    You can discard persistent connection at arbitrary timing with
+    <function>pgsql_fdw_disconnect()</function>.  It takes server oid and
+    user oid as arguments.  This function can handle only connections
+    established in current session; connections established by other backends
+    are not reachable.
+   </para>
+ 
+   <para>
+    You can discard all active and visible connections in current session with
+    using <structname>pgsql_fdw_connections</structname> and
+    <function>pgsql_fdw_disconnect()</function> together:
+ <synopsis>
+ postgres=# SELECT pgsql_fdw_disconnect(srvid, usesysid) FROM pgsql_fdw_connections;
+  pgsql_fdw_disconnect
+ ----------------------
+  OK
+  OK
+ (2 rows)
+ </synopsis>
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Transaction Management</title>
+   <para>
+    The <application>pgsql_fdw</application> begins remote transaction at the
+    beginning of a local query, and terminates it with <command>ABORT</command>
+    at the end of the local query.  This means that all foreign scans on a
+    foreign server in a local query are executed in one transaction.
+    If isolation level of local transaction is <literal>SERIALIZABLE</literal>,
+    <literal>SERIALIZABLE</literal> is used for remote transaction.  Otherwise,
+    if isolation level of local transaction is one of
+    <literal>READ UNCOMMITTED</literal>, <literal>READ COMMITTED</literal> or
+    <literal>REPEATABLE READ</literal>, then <literal>REPEATABLE READ</literal>
+    is used for remote transaction.
+    <literal>READ UNCOMMITTED</literal> and <literal>READ COMMITTED</literal>
+    are never used for remote transaction, because even
+    <literal>READ COMMITTED</literal> transaction might produce inconsistent
+    results, if remote data have been updated between two remote queries.
+   </para>
+   <para>
+    Note that even if the isolation level of local transaction was
+    <literal>SERIALIZABLE</literal> or <literal>REPEATABLE READ</literal>,
+    series of one query might produce different result, because foreign scans
+    in different local queries are executed in different remote transactions.
+    For instance, when client started a local transaction
+    explicitly with isolation level <literal>SERIALIZABLE</literal>, and
+    executed same local query which contains a foreign table which references
+    foreign data which is updated frequently, latter result would be different
+    from former result.
+   </para>
+   <para>
+    This restriction might be relaxed in future release.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Estimation of Costs and Rows</title>
+   <para>
+    The <application>pgsql_fdw</application> estimates the costs of a foreign
+    scan by adding up some basic costs:  connection costs, remote query costs
+    and data transfer costs.
+    To get remote query costs, <application>pgsql_fdw</application> executes
+    <command>EXPLAIN</command> command on remote server for each foreign scan.
+   </para>
+   <para>
+    On the other hand, estimated rows which was returned by
+    <command>EXPLAIN</command> is used for local estimation as-is.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>EXPLAIN Output</title>
+   <para>
+    For a foreign table using <literal>pgsql_fdw</>, <command>EXPLAIN</> shows
+    a remote SQL statement which is sent to remote
+    <productname>PostgreSQL</productname> server for a ForeignScan plan node.
+     For example:
+   </para>
+ <synopsis>
+ postgres=# EXPLAIN SELECT aid FROM pgbench_accounts WHERE abalance < 0;
+                                                         QUERY PLAN
+ --------------------------------------------------------------------------------------------------------------------------
+  Foreign Scan on pgbench_accounts  (cost=100.00..8105.13 rows=302613 width=8)
+    Filter: (abalance < 0)
+    Remote SQL: SELECT aid, NULL, abalance, NULL FROM public.pgbench_accounts
+ (3 rows)
+ </synopsis>
+   <para>
+    When you specify <literal>VERBOSE</> option, you can see actual DECLARE
+    statement with cursor name which is used for the scan.
+   </para>
+  </sect2>
+ 
+  <sect2>
+   <title>Author</title>
+   <para>
+    Shigeru Hanada <email>shigeru.hanada@gmail.com</email>
+   </para>
+  </sect2>
+ 
+ </sect1>

diff --git a/contrib/pgsql_fdw/deparse.c b/contrib/pgsql_fdw/deparse.c
index ca3356d..e7a6303 100644
*** a/contrib/pgsql_fdw/deparse.c
--- b/contrib/pgsql_fdw/deparse.c
***************
*** 14,19 ****
--- 14,21 ----
  
  #include "access/transam.h"
  #include "catalog/pg_class.h"
+ #include "catalog/pg_operator.h"
+ #include "catalog/pg_type.h"
  #include "commands/defrem.h"
  #include "foreign/foreign.h"
  #include "lib/stringinfo.h"
***************
*** 22,30 ****
--- 24,34 ----
  #include "nodes/makefuncs.h"
  #include "optimizer/clauses.h"
  #include "optimizer/var.h"
+ #include "parser/parser.h"
  #include "parser/parsetree.h"
  #include "utils/builtins.h"
  #include "utils/lsyscache.h"
+ #include "utils/syscache.h"
  
  #include "pgsql_fdw.h"
  
*************** static void deparseRelation(StringInfo b
*** 44,49 ****
--- 48,74 ----
  							bool need_prefix);
  static void deparseVar(StringInfo buf, Var *node, PlannerInfo *root,
  					   bool need_prefix);
+ static void deparseConst(StringInfo buf, Const *node, PlannerInfo *root);
+ static void deparseBoolExpr(StringInfo buf, BoolExpr *node, PlannerInfo *root);
+ static void deparseNullTest(StringInfo buf, NullTest *node, PlannerInfo *root);
+ static void deparseDistinctExpr(StringInfo buf, DistinctExpr *node,
+ 								PlannerInfo *root);
+ static void deparseRelabelType(StringInfo buf, RelabelType *node,
+ 							   PlannerInfo *root);
+ static void deparseFuncExpr(StringInfo buf, FuncExpr *node, PlannerInfo *root);
+ static void deparseParam(StringInfo buf, Param *node, PlannerInfo *root);
+ static void deparseScalarArrayOpExpr(StringInfo buf, ScalarArrayOpExpr *node,
+ 									 PlannerInfo *root);
+ static void deparseOpExpr(StringInfo buf, OpExpr *node, PlannerInfo *root);
+ static void deparseArrayRef(StringInfo buf, ArrayRef *node, PlannerInfo *root);
+ static void deparseArrayExpr(StringInfo buf, ArrayExpr *node, PlannerInfo *root);
+ 
+ /*
+  * Determine whether an expression can be evaluated on remote side safely.
+  */
+ static bool is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr);
+ static bool foreign_expr_walker(Node *node, foreign_executable_cxt *context);
+ static bool is_builtin(Oid procid);
  
  /*
   * Deparse query representation into SQL statement which suits for remote
*************** deparseSimpleSql(Oid relid,
*** 152,157 ****
--- 177,273 ----
  }
  
  /*
+  * Examine baserestrictinfo of baserel, and extract expressions which can be
+  * evaluated on remote side safely.  This function never changes
+  * baserestrictinfo.
+  */
+ List *
+ extractRemoteExprs(PlannerInfo *root,
+ 				   RelOptInfo *baserel,
+ 				   List **local_exprs)
+ {
+ 	ListCell	   *lc;
+ 	List		   *exprs = NIL;
+ 
+ 	foreach(lc, baserel->baserestrictinfo)
+ 	{
+ 		RestrictInfo *ri = (RestrictInfo *) lfirst(lc);
+ 
+ 		if (is_foreign_expr(root, baserel, ri->clause))
+ 			exprs = lappend(exprs, ri->clause);
+ 		else
+ 		{
+ 			if (local_exprs != NULL)
+ 				*local_exprs = lappend(*local_exprs, ri->clause);
+ 		}
+ 		
+ 	}
+ 
+ 	return exprs;
+ }
+ 
+ /*
+  * Deparse given expression into buf.  Actual string operation is delegated to
+  * node-type-specific functions.
+  *
+  * Note that switch statement of this function MUST match the one in
+  * foreign_expr_walker to avoid unsupported error..
+  */
+ void
+ deparseExpr(StringInfo buf, Expr *node, PlannerInfo *root)
+ {
+ 	/*
+ 	 * This part must be match foreign_expr_walker.
+ 	 */
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 			deparseConst(buf, (Const *) node, root);
+ 			break;
+ 		case T_BoolExpr:
+ 			deparseBoolExpr(buf, (BoolExpr *) node, root);
+ 			break;
+ 		case T_NullTest:
+ 			deparseNullTest(buf, (NullTest *) node, root);
+ 			break;
+ 		case T_DistinctExpr:
+ 			deparseDistinctExpr(buf, (DistinctExpr *) node, root);
+ 			break;
+ 		case T_RelabelType:
+ 			deparseRelabelType(buf, (RelabelType *) node, root);
+ 			break;
+ 		case T_FuncExpr:
+ 			deparseFuncExpr(buf, (FuncExpr *) node, root);
+ 			break;
+ 		case T_Param:
+ 			deparseParam(buf, (Param *) node, root);
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			deparseScalarArrayOpExpr(buf, (ScalarArrayOpExpr *) node, root);
+ 			break;
+ 		case T_OpExpr:
+ 			deparseOpExpr(buf, (OpExpr *) node, root);
+ 			break;
+ 		case T_Var:
+ 			deparseVar(buf, (Var *) node, root, false);
+ 			break;
+ 		case T_ArrayRef:
+ 			deparseArrayRef(buf, (ArrayRef *) node, root);
+ 			break;
+ 		case T_ArrayExpr:
+ 			deparseArrayExpr(buf, (ArrayExpr *) node, root);
+ 			break;
+ 		default:
+ 			{
+ 				ereport(ERROR,
+ 						(errmsg("unsupported expression for deparse"),
+ 						 errdetail("%s", nodeToString(node))));
+ 			}
+ 			break;
+ 	}
+ }
+ 
+ /*
   * Deparse node into buf, with relation qualifier if need_prefix was true.  If
   * node is a column of a foreign table, use value of colname FDW option (if any)
   * instead of attribute name.
*************** deparseRelation(StringInfo buf,
*** 287,289 ****
--- 403,1093 ----
  		appendStringInfo(buf, "%s.", q_nspname);
  	appendStringInfo(buf, "%s", q_relname);
  }
+ 
+ /*
+  * Deparse given constant value into buf.  This function have to be kept in
+  * sync with get_const_expr.
+  */
+ static void
+ deparseConst(StringInfo buf,
+ 			 Const *node,
+ 			 PlannerInfo *root)
+ {
+ 	Oid			typoutput;
+ 	bool		typIsVarlena;
+ 	char	   *extval;
+ 	bool		isfloat = false;
+ 	bool		needlabel;
+ 
+ 	if (node->constisnull)
+ 	{
+ 		appendStringInfo(buf, "NULL");
+ 		return;
+ 	}
+ 
+ 	getTypeOutputInfo(node->consttype,
+ 					  &typoutput, &typIsVarlena);
+ 	extval = OidOutputFunctionCall(typoutput, node->constvalue);
+ 
+ 	switch (node->consttype)
+ 	{
+ 		case ANYARRAYOID:
+ 		case ANYNONARRAYOID:
+ 			elog(ERROR, "anyarray and anyenum are not supported");
+ 			break;
+ 		case INT2OID:
+ 		case INT4OID:
+ 		case INT8OID:
+ 		case OIDOID:
+ 		case FLOAT4OID:
+ 		case FLOAT8OID:
+ 		case NUMERICOID:
+ 			{
+ 				/*
+ 				 * No need to quote unless they contain special values such as
+ 				 * 'Nan'.
+ 				 */
+ 				if (strspn(extval, "0123456789+-eE.") == strlen(extval))
+ 				{
+ 					if (extval[0] == '+' || extval[0] == '-')
+ 						appendStringInfo(buf, "(%s)", extval);
+ 					else
+ 						appendStringInfoString(buf, extval);
+ 					if (strcspn(extval, "eE.") != strlen(extval))
+ 						isfloat = true;	/* it looks like a float */
+ 				}
+ 				else
+ 					appendStringInfo(buf, "'%s'", extval);
+ 			}
+ 			break;
+ 		case BITOID:
+ 		case VARBITOID:
+ 			appendStringInfo(buf, "B'%s'", extval);
+ 			break;
+ 		case BOOLOID:
+ 			if (strcmp(extval, "t") == 0)
+ 				appendStringInfoString(buf, "true");
+ 			else
+ 				appendStringInfoString(buf, "false");
+ 			break;
+ 
+ 		default:
+ 			{
+ 				const char *valptr;
+ 
+ 				appendStringInfoChar(buf, '\'');
+ 				for (valptr = extval; *valptr; valptr++)
+ 				{
+ 					char		ch = *valptr;
+ 
+ 					/*
+ 					 * standard_conforming_strings of remote session should be
+ 					 * set to similar value as local session.
+ 					 */
+ 					if (SQL_STR_DOUBLE(ch, !standard_conforming_strings))
+ 						appendStringInfoChar(buf, ch);
+ 					appendStringInfoChar(buf, ch);
+ 				}
+ 				appendStringInfoChar(buf, '\'');
+ 			}
+ 			break;
+ 	}
+ 
+ 	/*
+ 	 * Append ::typename unless the constant will be implicitly typed as the
+ 	 * right type when it is read in.
+ 	 *
+ 	 * XXX this code has to be kept in sync with the behavior of the parser,
+ 	 * especially make_const.
+ 	 */
+ 	switch (node->consttype)
+ 	{
+ 		case BOOLOID:
+ 		case INT4OID:
+ 		case UNKNOWNOID:
+ 			needlabel = false;
+ 			break;
+ 		case NUMERICOID:
+ 			needlabel = !isfloat || (node->consttypmod >= 0);
+ 			break;
+ 		default:
+ 			needlabel = true;
+ 			break;
+ 	}
+ 	if (needlabel)
+ 	{
+ 		appendStringInfo(buf, "::%s",
+ 						 format_type_with_typemod(node->consttype,
+ 												  node->consttypmod));
+ 	}
+ }
+ 
+ static void
+ deparseBoolExpr(StringInfo buf,
+ 				BoolExpr *node,
+ 				PlannerInfo *root)
+ {
+ 	ListCell   *lc;
+ 	char	   *op;
+ 	bool		first;
+ 
+ 	switch (node->boolop)
+ 	{
+ 		case AND_EXPR:
+ 			op = "AND";
+ 			break;
+ 		case OR_EXPR:
+ 			op = "OR";
+ 			break;
+ 		case NOT_EXPR:
+ 			appendStringInfo(buf, "(NOT ");
+ 			deparseExpr(buf, list_nth(node->args, 0), root);
+ 			appendStringInfo(buf, ")");
+ 			return;
+ 	}
+ 
+ 	first = true;
+ 	appendStringInfo(buf, "(");
+ 	foreach(lc, node->args)
+ 	{
+ 		if (!first)
+ 			appendStringInfo(buf, " %s ", op);
+ 		deparseExpr(buf, (Expr *) lfirst(lc), root);
+ 		first = false;
+ 	}
+ 	appendStringInfo(buf, ")");
+ }
+ 
+ /*
+  * Deparse given IS [NOT] NULL test expression into buf.
+  */
+ static void
+ deparseNullTest(StringInfo buf,
+ 				NullTest *node,
+ 				PlannerInfo *root)
+ {
+ 	appendStringInfoChar(buf, '(');
+ 	deparseExpr(buf, node->arg, root);
+ 	if (node->nulltesttype == IS_NULL)
+ 		appendStringInfo(buf, " IS NULL)");
+ 	else
+ 		appendStringInfo(buf, " IS NOT NULL)");
+ }
+ 
+ static void
+ deparseDistinctExpr(StringInfo buf,
+ 					DistinctExpr *node,
+ 					PlannerInfo *root)
+ {
+ 	Assert(list_length(node->args) == 2);
+ 
+ 	deparseExpr(buf, linitial(node->args), root);
+ 	appendStringInfo(buf, " IS DISTINCT FROM ");
+ 	deparseExpr(buf, lsecond(node->args), root);
+ }
+ 
+ static void
+ deparseRelabelType(StringInfo buf,
+ 				   RelabelType *node,
+ 				   PlannerInfo *root)
+ {
+ 	char	   *typname;
+ 
+ 	Assert(node->arg);
+ 
+ 	/* We don't need to deparse cast when argument has same type as result. */
+ 	if (IsA(node->arg, Const) &&
+ 		((Const *) node->arg)->consttype == node->resulttype &&
+ 		((Const *) node->arg)->consttypmod == -1)
+ 	{
+ 		deparseExpr(buf, node->arg, root);
+ 		return;
+ 	}
+ 
+ 	typname = format_type_with_typemod(node->resulttype, node->resulttypmod);
+ 	appendStringInfoChar(buf, '(');
+ 	deparseExpr(buf, node->arg, root);
+ 	appendStringInfo(buf, ")::%s", typname);
+ }
+ 
+ /*
+  * Deparse given node which represents a function call into buf.  We treat only
+  * explicit function call and explicit cast (coerce), because others are
+  * processed on remote side if necessary.
+  *
+  * Function name (and type name) is always qualified by schema name to avoid
+  * problems caused by different setting of search_path on remote side.
+  */
+ static void
+ deparseFuncExpr(StringInfo buf,
+ 				FuncExpr *node,
+ 				PlannerInfo *root)
+ {
+ 	Oid				pronamespace;
+ 	const char	   *schemaname;
+ 	const char	   *funcname;
+ 	ListCell	   *arg;
+ 	bool			first;
+ 
+ 	pronamespace = get_func_namespace(node->funcid);
+ 	schemaname = quote_identifier(get_namespace_name(pronamespace));
+ 	funcname = quote_identifier(get_func_name(node->funcid));
+ 
+ 	if (node->funcformat == COERCE_EXPLICIT_CALL)
+ 	{
+ 		/* Function call, deparse all arguments recursively. */
+ 		appendStringInfo(buf, "%s.%s(", schemaname, funcname);
+ 		first = true;
+ 		foreach(arg, node->args)
+ 		{
+ 			if (!first)
+ 				appendStringInfo(buf, ", ");
+ 			deparseExpr(buf, lfirst(arg), root);
+ 			first = false;
+ 		}
+ 		appendStringInfoChar(buf, ')');
+ 	}
+ 	else if (node->funcformat == COERCE_EXPLICIT_CAST)
+ 	{
+ 		/* Explicit cast, deparse only first argument. */
+ 		appendStringInfoChar(buf, '(');
+ 		deparseExpr(buf, linitial(node->args), root);
+ 		appendStringInfo(buf, ")::%s", funcname);
+ 	}
+ 	else
+ 	{
+ 		/* Implicit cast, deparse only first argument. */
+ 		deparseExpr(buf, linitial(node->args), root);
+ 	}
+ }
+ 
+ /*
+  * Deparse given Param node into buf.
+  *
+  * We don't renumber parameter id, because skipping $1 is not cause problem
+  * as far as we pass through all arguments.
+  */
+ static void
+ deparseParam(StringInfo buf,
+ 			 Param *node,
+ 			 PlannerInfo *root)
+ {
+ 	Assert(node->paramkind == PARAM_EXTERN);
+ 
+ 	appendStringInfo(buf, "$%d", node->paramid);
+ }
+ 
+ /*
+  * Deparse given ScalarArrayOpExpr expression into buf.  To avoid problems
+  * around priority of operations, we always parenthesize the arguments.  Also we
+  * use OPERATOR(schema.operator) notation to determine remote operator exactly.
+  */
+ static void
+ deparseScalarArrayOpExpr(StringInfo buf,
+ 						 ScalarArrayOpExpr *node,
+ 						 PlannerInfo *root)
+ {
+ 	HeapTuple	tuple;
+ 	Form_pg_operator form;
+ 	const char *opnspname;
+ 	char	   *opname;
+ 	Expr	   *arg1;
+ 	Expr	   *arg2;
+ 
+ 	/* Retrieve necessary information about the operator from system catalog. */
+ 	tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(node->opno));
+ 	if (!HeapTupleIsValid(tuple))
+ 		elog(ERROR, "cache lookup failed for operator %u", node->opno);
+ 	form = (Form_pg_operator) GETSTRUCT(tuple);
+ 	/* opname is not a SQL identifier, so we don't need to quote it. */
+ 	opname = NameStr(form->oprname);
+ 	opnspname = quote_identifier(get_namespace_name(form->oprnamespace));
+ 	ReleaseSysCache(tuple);
+ 
+ 	/* Sanity check. */
+ 	Assert(list_length(node->args) == 2);
+ 
+ 	/* Always parenthesize the expression. */
+ 	appendStringInfoChar(buf, '(');
+ 
+ 	/* Extract operands. */
+ 	arg1 = linitial(node->args);
+ 	arg2 = lsecond(node->args);
+ 
+ 	/* Deparse fully qualified operator name. */
+ 	deparseExpr(buf, arg1, root);
+ 	appendStringInfo(buf, " OPERATOR(%s.%s) %s (",
+ 					 opnspname, opname, node->useOr ? "ANY" : "ALL");
+ 	deparseExpr(buf, arg2, root);
+ 	appendStringInfoChar(buf, ')');
+ 
+ 	/* Always parenthesize the expression. */
+ 	appendStringInfoChar(buf, ')');
+ }
+ 
+ /*
+  * Deparse given operator expression into buf.  To avoid problems around
+  * priority of operations, we always parenthesize the arguments.  Also we use
+  * OPERATOR(schema.operator) notation to determine remote operator exactly.
+  */
+ static void
+ deparseOpExpr(StringInfo buf,
+ 			  OpExpr *node,
+ 			  PlannerInfo *root)
+ {
+ 	HeapTuple	tuple;
+ 	Form_pg_operator form;
+ 	const char *opnspname;
+ 	char	   *opname;
+ 	char		oprkind;
+ 	ListCell   *arg;
+ 
+ 	/* Retrieve necessary information about the operator from system catalog. */
+ 	tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(node->opno));
+ 	if (!HeapTupleIsValid(tuple))
+ 		elog(ERROR, "cache lookup failed for operator %u", node->opno);
+ 	form = (Form_pg_operator) GETSTRUCT(tuple);
+ 	opnspname = quote_identifier(get_namespace_name(form->oprnamespace));
+ 	/* opname is not a SQL identifier, so we don't need to quote it. */
+ 	opname = NameStr(form->oprname);
+ 	oprkind = form->oprkind;
+ 	ReleaseSysCache(tuple);
+ 
+ 	/* Sanity check. */
+ 	Assert((oprkind == 'r' && list_length(node->args) == 1) ||
+ 		   (oprkind == 'l' && list_length(node->args) == 1) ||
+ 		   (oprkind == 'b' && list_length(node->args) == 2));
+ 
+ 	/* Always parenthesize the expression. */
+ 	appendStringInfoChar(buf, '(');
+ 
+ 	/* Deparse first operand. */
+ 	arg = list_head(node->args);
+ 	if (oprkind == 'r' || oprkind == 'b')
+ 	{
+ 		deparseExpr(buf, lfirst(arg), root);
+ 		appendStringInfoChar(buf, ' ');
+ 	}
+ 
+ 	/* Deparse fully qualified operator name. */
+ 	appendStringInfo(buf, "OPERATOR(%s.%s)", opnspname, opname);
+ 
+ 	/* Deparse last operand. */
+ 	arg = list_tail(node->args);
+ 	if (oprkind == 'l' || oprkind == 'b')
+ 	{
+ 		appendStringInfoChar(buf, ' ');
+ 		deparseExpr(buf, lfirst(arg), root);
+ 	}
+ 
+ 	appendStringInfoChar(buf, ')');
+ }
+ 
+ static void
+ deparseArrayRef(StringInfo buf,
+ 				ArrayRef *node,
+ 				PlannerInfo *root)
+ {
+ 	ListCell	   *lowlist_item;
+ 	ListCell	   *uplist_item;
+ 
+ 	/* Always parenthesize the expression. */
+ 	appendStringInfoChar(buf, '(');
+ 
+ 	/* Deparse referenced array expression first. */
+ 	appendStringInfoChar(buf, '(');
+ 	deparseExpr(buf, node->refexpr, root);
+ 	appendStringInfoChar(buf, ')');
+ 
+ 	/* Deparse subscripts expression. */
+ 	lowlist_item = list_head(node->reflowerindexpr);	/* could be NULL */
+ 	foreach(uplist_item, node->refupperindexpr)
+ 	{
+ 		appendStringInfoChar(buf, '[');
+ 		if (lowlist_item)
+ 		{
+ 			deparseExpr(buf, lfirst(lowlist_item), root);
+ 			appendStringInfoChar(buf, ':');
+ 			lowlist_item = lnext(lowlist_item);
+ 		}
+ 		deparseExpr(buf, lfirst(uplist_item), root);
+ 		appendStringInfoChar(buf, ']');
+ 	}
+ 
+ 	appendStringInfoChar(buf, ')');
+ }
+ 
+ 
+ /*
+  * Deparse given array of something into buf.
+  */
+ static void
+ deparseArrayExpr(StringInfo buf,
+ 				 ArrayExpr *node,
+ 				 PlannerInfo *root)
+ {
+ 	ListCell	   *lc;
+ 	bool			first = true;
+ 
+ 	appendStringInfo(buf, "ARRAY[");
+ 	foreach(lc, node->elements)
+ 	{
+ 		if (!first)
+ 			appendStringInfo(buf, ", ");
+ 		deparseExpr(buf, lfirst(lc), root);
+ 
+ 		first = false;
+ 	}
+ 	appendStringInfoChar(buf, ']');
+ 
+ 	/* If the array is empty, we need explicit cast to the array type. */
+ 	if (node->elements == NIL)
+ 	{
+ 		char	   *typname;
+ 
+ 		typname = format_type_with_typemod(node->array_typeid, -1);
+ 		appendStringInfo(buf, "::%s", typname);
+ 	}
+ }
+ 
+ /*
+  * Returns true if expr is safe to be evaluated on the foreign server.
+  */
+ static bool
+ is_foreign_expr(PlannerInfo *root, RelOptInfo *baserel, Expr *expr)
+ {
+ 	foreign_executable_cxt	context;
+ 	context.root = root;
+ 	context.foreignrel = baserel;
+ 
+ 	/*
+ 	 * An expression which includes any mutable function can't be pushed down
+ 	 * because it's result is not stable.  For example, pushing now() down to
+ 	 * remote side would cause confusion from the clock offset.
+ 	 * If we have routine mapping infrastructure in future release, we will be
+ 	 * able to choose function to be pushed down in finer granularity.
+ 	 */
+ 	if (contain_mutable_functions((Node *) expr))
+ 		return false;
+ 
+ 	/*
+ 	 * Check that the expression consists of nodes which are known as safe to
+ 	 * be pushed down.
+ 	 */
+ 	if (foreign_expr_walker((Node *) expr, &context))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ /*
+  * Return true if node includes any node which is not known as safe to be
+  * pushed down.
+  */
+ static bool
+ foreign_expr_walker(Node *node, foreign_executable_cxt *context)
+ {
+ 	if (node == NULL)
+ 		return false;
+ 
+ 	/*
+ 	 * Special case handling for List; expression_tree_walker handles List as
+ 	 * well as other Expr nodes.  For instance, List is used in RestrictInfo
+ 	 * for args of FuncExpr node.
+ 	 *
+ 	 * Although the comments of expression_tree_walker mention that
+ 	 * RangeTblRef, FromExpr, JoinExpr, and SetOperationStmt are handled as
+ 	 * well, but we don't care them because they are not used in RestrictInfo.
+ 	 * If one of them was passed into, default label catches it and give up
+ 	 * traversing.
+ 	 */
+ 	if (IsA(node, List))
+ 	{
+ 		ListCell	   *lc;
+ 
+ 		foreach(lc, (List *) node)
+ 		{
+ 			if (foreign_expr_walker(lfirst(lc), context))
+ 				return true;
+ 		}
+ 		return false;
+ 	}
+ 
+ 	/*
+ 	 * If given expression has valid collation, it can't be pushed down because
+ 	 * it might has incompatible semantics on remote side.
+ 	 */
+ 	if (exprCollation(node) != InvalidOid ||
+ 		exprInputCollation(node) != InvalidOid)
+ 		return true;
+ 
+ 	/*
+ 	 * If return type of given expression is not built-in, it can't be pushed
+ 	 * down because it might has incompatible semantics on remote side.
+ 	 */
+ 	if (!is_builtin(exprType(node)))
+ 		return true;
+ 
+ 	switch (nodeTag(node))
+ 	{
+ 		case T_Const:
+ 			/*
+ 			 * Using anyarray and/or anyenum in remote query is not supported.
+ 			 */
+ 			if (((Const *) node)->consttype == ANYARRAYOID ||
+ 				((Const *) node)->consttype == ANYNONARRAYOID)
+ 				return true;
+ 			break;
+ 		case T_BoolExpr:
+ 		case T_NullTest:
+ 		case T_DistinctExpr:
+ 		case T_RelabelType:
+ 			/*
+ 			 * These type of nodes are known as safe to be pushed down.
+ 			 * Of course the subtree of the node, if any, should be checked
+ 			 * continuously at the tail of this function.
+ 			 */
+ 			break;
+ 		/*
+ 		 * If function used by the expression is not built-in, it can't be
+ 		 * pushed down because it might has incompatible semantics on remote
+ 		 * side.
+ 		 */
+ 		case T_FuncExpr:
+ 			{
+ 				FuncExpr	   *fe = (FuncExpr *) node;
+ 				if (!is_builtin(fe->funcid))
+ 					return true;
+ 			}
+ 			break;
+ 		case T_Param:
+ 			/*
+ 			 * Only external parameters can be pushed down.:
+ 			 */
+ 			{
+ 				if (((Param *) node)->paramkind != PARAM_EXTERN)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ScalarArrayOpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				ScalarArrayOpExpr   *oe = (ScalarArrayOpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_OpExpr:
+ 			/*
+ 			 * Only built-in operators can be pushed down.  In addition,
+ 			 * underlying function must be built-in and immutable, but we don't
+ 			 * check volatility here; such check must be done already with
+ 			 * contain_mutable_functions.
+ 			 */
+ 			{
+ 				OpExpr	   *oe = (OpExpr *) node;
+ 
+ 				if (!is_builtin(oe->opno) || !is_builtin(oe->opfuncid))
+ 					return true;
+ 
+ 				/* operands are checked later */
+ 			}
+ 			break;
+ 		case T_Var:
+ 			/*
+ 			 * Var can be pushed down if it is in the foreign table.
+ 			 * XXX Var of other relation can be here?
+ 			 */
+ 			{
+ 				Var	   *var = (Var *) node;
+ 				foreign_executable_cxt *f_context;
+ 
+ 				f_context = (foreign_executable_cxt *) context;
+ 				if (var->varno != f_context->foreignrel->relid ||
+ 					var->varlevelsup != 0)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayRef:
+ 			/*
+ 			 * ArrayRef which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				ArrayRef	   *ar = (ArrayRef *) node;;
+ 
+ 				if (!is_builtin(ar->refelemtype))
+ 					return true;
+ 
+ 				/* Assignment should not be in restrictions. */
+ 				if (ar->refassgnexpr != NULL)
+ 					return true;
+ 			}
+ 			break;
+ 		case T_ArrayExpr:
+ 			/*
+ 			 * ArrayExpr which holds non-built-in typed elements can't be pushed
+ 			 * down.
+ 			 */
+ 			{
+ 				if (!is_builtin(((ArrayExpr *) node)->element_typeid))
+ 					return true;
+ 			}
+ 			break;
+ 		default:
+ 			{
+ 				ereport(DEBUG3,
+ 						(errmsg("expression is too complex"),
+ 						 errdetail("%s", nodeToString(node))));
+ 				return true;
+ 			}
+ 			break;
+ 	}
+ 
+ 	return expression_tree_walker(node, foreign_expr_walker, context);
+ }
+ 
+ /*
+  * Return true if given object is one of built-in objects.
+  */
+ static bool
+ is_builtin(Oid oid)
+ {
+ 	return (oid < FirstNormalObjectId);
+ }
+ 
+ /*
+  * Deparse exprs to WHERE clause string and append it into buf.
+  *
+  * Each element in exprs must be a boolean expression.
+  */
+ void
+ deparseWhereClause(StringInfo buf,
+ 				   List *exprs,
+ 				   PlannerInfo *root)
+ {
+ 	ListCell	   *lc;
+ 	bool			first = true;
+ 
+ 	appendStringInfo(buf, " WHERE (");
+ 	foreach(lc, exprs)
+ 	{
+ 		Expr	   *expr = (Expr *) lfirst(lc);
+ 
+ 		/* Connect expressions with "AND". */
+ 		if (!first)
+ 			appendStringInfo(buf, ") AND (");
+ 	
+ 		deparseExpr(buf, expr, root);
+ 		first = false;
+ 	}
+ 	appendStringInfoChar(buf, ')');
+ }
diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index fdd908c..5560931 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.
*** 230,241 ****
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                     QUERY PLAN                                                    
! ------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: ((t1.c1 = 101) AND ((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
--- 230,241 ----
  
  -- with WHERE clause
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
!                                                                          QUERY PLAN                                                                          
! -------------------------------------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on public.ft1 t1
     Output: c1, c2, c3, c4, c5, c6, c7
!    Filter: (((t1.c6)::text = '1'::text) AND (t1.c7 = '1'::bpchar))
!    Remote SQL: DECLARE pgsql_fdw_cursor_4 SCROLL CURSOR FOR SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 101))
  (4 rows)
  
  SELECT * FROM ft1 t1 WHERE t1.c1 = 101 AND t1.c6 = '1' AND t1.c7 = '1';
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 343,362 ****
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = abs(c2))
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = c2)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- ===================================================================
  -- parameterized queries
--- 343,433 ----
  (3 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
!                                                           QUERY PLAN                                                           
! -------------------------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) pg_catalog.abs(c2)))
! (2 rows)
  
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
!                                                   QUERY PLAN                                                   
! ---------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) c2))
! (2 rows)
! 
! -- ===================================================================
! -- WHERE push down
! -- ===================================================================
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 1;         -- Var, OpExpr(b), Const
!                                                   QUERY PLAN                                                  
! --------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 100 AND t1.c2 = 0; -- BoolExpr
!                                                                      QUERY PLAN                                                                     
! ----------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 100)) AND ((c2 OPERATOR(pg_catalog.=) 0))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 IS NULL;        -- NullTest
!                                          QUERY PLAN                                          
! ---------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" IS NULL))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 IS NOT NULL;    -- NullTest
!                                            QUERY PLAN                                            
! -------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" IS NOT NULL))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE round(abs(c1), 0) = 1; -- FuncExpr
!                                                                          QUERY PLAN                                                                         
! ------------------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ((pg_catalog.round(pg_catalog.abs("C 1"), 0) OPERATOR(pg_catalog.=) 1::numeric))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 = -c1;          -- OpExpr(l)
!                                                                 QUERY PLAN                                                                 
! -------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) (OPERATOR(pg_catalog.-) "C 1")))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE 1 = c1!;           -- OpExpr(r)
!                                                                    QUERY PLAN                                                                   
! ------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE ((1::numeric OPERATOR(pg_catalog.=) ("C 1" OPERATOR(pg_catalog.!))))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE (c1 IS NOT NULL) IS DISTINCT FROM (c1 IS NOT NULL); -- DistinctExpr
!                                                               QUERY PLAN                                                              
! --------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" IS NOT NULL) IS DISTINCT FROM ("C 1" IS NOT NULL))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 = ANY(ARRAY[c2, 1, c1 + 0]); -- ScalarArrayOpExpr
!                                                                            QUERY PLAN                                                                            
! -----------------------------------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) ANY (ARRAY[c2, 1, ("C 1" OPERATOR(pg_catalog.+) 0)])))
! (2 rows)
! 
! EXPLAIN (COSTS false) SELECT * FROM ft1 ft WHERE c1 = (ARRAY[c1,c2,3])[1]; -- ArrayRef
!                                                               QUERY PLAN                                                               
! ---------------------------------------------------------------------------------------------------------------------------------------
!  Foreign Scan on ft1 ft
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) ((ARRAY["C 1", c2, 3])[1])))
! (2 rows)
  
  -- ===================================================================
  -- parameterized queries
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 364,379 ****
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                      QUERY PLAN                                      
! -------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Filter: (c1 = 1)
!          Remote SQL: SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
     ->  Foreign Scan on ft2 t2
!          Filter: (c1 = 2)
!          Remote SQL: SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1"
! (7 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
--- 435,448 ----
  -- simple join
  PREPARE st1(int, int) AS SELECT t1.c3, t2.c3 FROM ft1 t1, ft2 t2 WHERE t1.c1 = $1 AND t2.c1 = $2;
  EXPLAIN (COSTS false) EXECUTE st1(1, 2);
!                                                           QUERY PLAN                                                          
! ------------------------------------------------------------------------------------------------------------------------------
   Nested Loop
     ->  Foreign Scan on ft1 t1
!          Remote SQL: SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
     ->  Foreign Scan on ft2 t2
!          Remote SQL: SELECT "C 1", NULL, c3, NULL, NULL, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 2))
! (5 rows)
  
  EXECUTE st1(1, 1);
    c3   |  c3   
*************** EXECUTE st1(101, 101);
*** 390,409 ****
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                            QUERY PLAN                                           
! ------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Semi Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  Foreign Scan on ft2 t2
!                      Filter: ((c1 > 10) AND (date_part('dow'::text, c4) = 6::double precision))
!                      Remote SQL: SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1"
! (11 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 459,477 ----
  -- subquery using stable function (can't be pushed down)
  PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c4) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st2(10, 20);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Semi Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.<) 20))
           ->  Hash
                 ->  Foreign Scan on ft2 t2
!                      Filter: (date_part('dow'::text, c4) = 6::double precision)
!                      Remote SQL: SELECT "C 1", NULL, c3, c4, NULL, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.>) 10))
! (10 rows)
  
  EXECUTE st2(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st1(101, 101);
*** 420,439 ****
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                            QUERY PLAN                                           
! ------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Semi Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Filter: (c1 < 20)
!                Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
           ->  Hash
                 ->  Foreign Scan on ft2 t2
!                      Filter: ((c1 > 10) AND (date_part('dow'::text, c5) = 6::double precision))
!                      Remote SQL: SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1"
! (11 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
--- 488,506 ----
  -- subquery using immutable function (can be pushed down)
  PREPARE st3(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN (SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND EXTRACT(dow FROM c5) = 6) ORDER BY c1;
  EXPLAIN (COSTS false) EXECUTE st3(10, 20);
!                                                                QUERY PLAN                                                                
! -----------------------------------------------------------------------------------------------------------------------------------------
   Sort
     Sort Key: t1.c1
     ->  Hash Semi Join
           Hash Cond: (t1.c3 = t2.c3)
           ->  Foreign Scan on ft1 t1
!                Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.<) 20))
           ->  Hash
                 ->  Foreign Scan on ft2 t2
!                      Filter: (date_part('dow'::text, c5) = 6::double precision)
!                      Remote SQL: SELECT "C 1", NULL, c3, NULL, c5, NULL, NULL FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.>) 10))
! (10 rows)
  
  EXECUTE st3(10, 20);
   c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     
*************** EXECUTE st3(20, 30);
*** 450,501 ****
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = 1)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                              QUERY PLAN                              
! ---------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Filter: (c1 = $1)
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1"
! (3 rows)
  
  -- cleanup
  DEALLOCATE st1;
--- 517,562 ----
  -- custom plan should be chosen
  PREPARE st4(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 = $1;
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                   QUERY PLAN                                                  
! --------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                   QUERY PLAN                                                  
! --------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                   QUERY PLAN                                                  
! --------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                   QUERY PLAN                                                  
! --------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                   QUERY PLAN                                                  
! --------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) 1))
! (2 rows)
  
  EXPLAIN (COSTS false) EXECUTE st4(1);
!                                                   QUERY PLAN                                                   
! ---------------------------------------------------------------------------------------------------------------
   Foreign Scan on ft1 t1
!    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7 FROM "S 1"."T 1" WHERE (("C 1" OPERATOR(pg_catalog.=) $1))
! (2 rows)
  
  -- cleanup
  DEALLOCATE st1;
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index df7f407..4916a45 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 17,26 ****
  #include "catalog/pg_foreign_table.h"
  #include "commands/defrem.h"
  #include "commands/explain.h"
! #include "foreign/fdwapi.h"
  #include "funcapi.h"
  #include "miscadmin.h"
- #include "nodes/nodeFuncs.h"
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.h"
  #include "optimizer/planmain.h"
--- 17,25 ----
  #include "catalog/pg_foreign_table.h"
  #include "commands/defrem.h"
  #include "commands/explain.h"
! #include "foreign/foreign.h"
  #include "funcapi.h"
  #include "miscadmin.h"
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.h"
  #include "optimizer/planmain.h"
*************** PG_MODULE_MAGIC;
*** 61,66 ****
--- 60,70 ----
  #define	CURSOR_NAME_FORMAT		"pgsql_fdw_cursor_%u"
  static uint32 cursor_id = 0;
  
+ /* Convenient macros for accessing the first record of PGresult. */
+ #define PGRES_VAL0(col)		(PQgetvalue(res, 0, (col)))
+ #define PGRES_NULL0(col)	(PQgetisnull(res, 0, (col)))
+ 
+ 
  /*
   * Index of FDW-private information stored in fdw_private list.
   *
*************** static uint32 cursor_id = 0;
*** 68,78 ****
   * the boundary between planner and executor.  Finally FdwPlan using cursor
   * would hold items below:
   *
!  * 1) plain SELECT statement
!  * 2) SQL statement used to declare cursor
!  * 3) SQL statement used to fetch rows from cursor
   * 5) SQL statement used to reset cursor
!  * 5) SQL statement used to close cursor
   *
   * These items are indexed with the enum FdwPrivateIndex, so an item
   * can be accessed directly via list_nth().  For example of FETCH
--- 72,83 ----
   * the boundary between planner and executor.  Finally FdwPlan using cursor
   * would hold items below:
   *
!  * 1) expressions which are pushed down
!  * 2) plain SELECT statement
!  * 3) SQL statement used to declare cursor
!  * 4) SQL statement used to fetch rows from cursor
   * 5) SQL statement used to reset cursor
!  * 6) SQL statement used to close cursor
   *
   * These items are indexed with the enum FdwPrivateIndex, so an item
   * can be accessed directly via list_nth().  For example of FETCH
*************** static uint32 cursor_id = 0;
*** 80,85 ****
--- 85,93 ----
   *      list_nth(fdw_private, FdwPrivateFetchSql)
   */
  enum FdwPrivateIndex {
+ 	/* Planning information */
+ 	FdwPrivateFdwExprs,
+ 
  	/* SQL statements */
  	FdwPrivateSelectSql,
  	FdwPrivateDeclareSql,
*************** pgsqlGetForeignPlan(PlannerInfo *root,
*** 282,298 ****
  	DefElem		   *def;
  	int				fetch_count = DEFAULT_FETCH_COUNT;
  	char		   *sql;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/*
! 	 * We have no native ability to evaluate restriction clauses, so we just
! 	 * put all the scan_clauses into the plan node's qual list for the
! 	 * executor to check.  So all we have to do here is strip RestrictInfo
! 	 * nodes from the clauses and ignore pseudoconstants (which will be
! 	 * handled elsewhere).
  	 */
  	scan_clauses = extract_actual_clauses(scan_clauses, false);
  
  	/*
  	 * Use specified fetch_count instead of default value, if any.  Foreign
--- 290,312 ----
  	DefElem		   *def;
  	int				fetch_count = DEFAULT_FETCH_COUNT;
  	char		   *sql;
+ 	List		   *fdw_exprs = NIL;
+ 	List		   *local_exprs = NIL;
  	ForeignTable   *table;
  	ForeignServer  *server;
  
  	/*
! 	 * We have native ability to evaluate restriction clauses on remote side,
! 	 * so we split clauses into local portion and remote portion.  Before
! 	 * that, we strip RestrictInfo nodes from the clauses and ignore
! 	 * pseudoconstants (which will be handled elsewhere).
! 	 *
! 	 * Extracted list of expressions is stored in fdw_private of ForeignScan
! 	 * for possible reference in executor handlers.
  	 */
  	scan_clauses = extract_actual_clauses(scan_clauses, false);
+ 	fdw_exprs = extractRemoteExprs(root, baserel, &local_exprs);
+ 	fdw_private = lappend(fdw_private, fdw_exprs);
  
  	/*
  	 * Use specified fetch_count instead of default value, if any.  Foreign
*************** pgsqlGetForeignPlan(PlannerInfo *root,
*** 322,330 ****
  	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
  
  	/*
! 	 * Construct simple remote query which has no WHERE clause.
  	 */
  	sql = deparseSimpleSql(foreigntableid, root, baserel, table);
  	fdw_private = lappend(fdw_private, makeString(sql));
  
  	/* Construct cursor name from sequential value */
--- 336,354 ----
  	elog(DEBUG1, "relid=%u fetch_count=%d", foreigntableid, fetch_count);
  
  	/*
! 	 * Construct remote query, and add WHERE clause if we have any expression
! 	 * which can be pushed down to remote side safely.
  	 */
  	sql = deparseSimpleSql(foreigntableid, root, baserel, table);
+ 	if (list_length(fdw_exprs) > 0)
+ 	{
+ 		StringInfoData	buf;
+ 
+ 		initStringInfo(&buf);
+ 		appendStringInfo(&buf, "%s", sql);
+ 		deparseWhereClause(&buf, fdw_exprs, root);
+ 		sql = buf.data;
+ 	}
  	fdw_private = lappend(fdw_private, makeString(sql));
  
  	/* Construct cursor name from sequential value */
*************** pgsqlGetForeignPlan(PlannerInfo *root,
*** 350,360 ****
  	appendStringInfo(&cursor, "CLOSE %s", name);
  	fdw_private = lappend(fdw_private, makeString(cursor.data));
  
! 	/* Create the ForeignScan node with fdw_private of selected path. */
  	return make_foreignscan(tlist,
! 							scan_clauses,
  							scan_relid,
! 							NIL,
  							fdw_private);
  }
  
--- 374,393 ----
  	appendStringInfo(&cursor, "CLOSE %s", name);
  	fdw_private = lappend(fdw_private, makeString(cursor.data));
  
! 	/*
! 	 * Create the ForeignScan node from target list, local filtering
! 	 * expressions, remote filtering expressions, and FDW private information.
! 	 *
! 	 * We remove expressions which are evaluated on remote side from qual of
! 	 * the scan node to avoid redundant filtering.  Such filter reduction
! 	 * can be done only here, done after choosing best path, because
! 	 * baserestrictinfo in RelOptInfo is shared by all possible paths until
! 	 * best path is chosen.
! 	 */
  	return make_foreignscan(tlist,
! 							local_exprs,
  							scan_relid,
! 							fdw_exprs,
  							fdw_private);
  }
  
diff --git a/contrib/pgsql_fdw/pgsql_fdw.h b/contrib/pgsql_fdw/pgsql_fdw.h
index 6eb99d5..5bd672a 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.h
--- b/contrib/pgsql_fdw/pgsql_fdw.h
***************
*** 15,20 ****
--- 15,21 ----
  #define PGSQL_FDW_H
  
  #include "postgres.h"
+ #include "foreign/fdwapi.h"
  #include "foreign/foreign.h"
  #include "nodes/relation.h"
  
*************** char *deparseSimpleSql(Oid relid,
*** 28,32 ****
--- 29,42 ----
  					   PlannerInfo *root,
  					   RelOptInfo *baserel,
  					   ForeignTable *table);
+ void deparseWhereClause(StringInfo buf,
+ 						List *exprs,
+ 						PlannerInfo *root);
+ List *extractRemoteExprs(PlannerInfo *root,
+ 						 RelOptInfo *baserel,
+ 						 List **local_exprs);
+ void deparseExpr(StringInfo buf,
+ 				 Expr *expr,
+ 				 PlannerInfo *root);
  
  #endif /* PGSQL_FDW_H */
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index b3fac96..b7cd71d 100644
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
*************** EXPLAIN (COSTS false) SELECT * FROM ft1 
*** 182,187 ****
--- 182,201 ----
  EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
  
  -- ===================================================================
+ -- WHERE push down
+ -- ===================================================================
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 1;         -- Var, OpExpr(b), Const
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = 100 AND t1.c2 = 0; -- BoolExpr
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 IS NULL;        -- NullTest
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 IS NOT NULL;    -- NullTest
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE round(abs(c1), 0) = 1; -- FuncExpr
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 = -c1;          -- OpExpr(l)
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE 1 = c1!;           -- OpExpr(r)
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE (c1 IS NOT NULL) IS DISTINCT FROM (c1 IS NOT NULL); -- DistinctExpr
+ EXPLAIN (COSTS false) SELECT * FROM ft1 t1 WHERE c1 = ANY(ARRAY[c2, 1, c1 + 0]); -- ScalarArrayOpExpr
+ EXPLAIN (COSTS false) SELECT * FROM ft1 ft WHERE c1 = (ARRAY[c1,c2,3])[1]; -- ArrayRef
+ 
+ -- ===================================================================
  -- parameterized queries
  -- ===================================================================
  -- simple join

diff --git a/contrib/pgsql_fdw/expected/pgsql_fdw.out b/contrib/pgsql_fdw/expected/pgsql_fdw.out
index 5560931..bd6aa73 100644
*** a/contrib/pgsql_fdw/expected/pgsql_fdw.out
--- b/contrib/pgsql_fdw/expected/pgsql_fdw.out
*************** INSERT INTO "S 1"."T 2"
*** 75,80 ****
--- 75,81 ----
  	       'AAA' || to_char(id, 'FM000')
  	FROM generate_series(1, 100) id;
  COMMIT;
+ ANALYZE "S 1"."T 1";
  -- ===================================================================
  -- tests for pgsql_fdw_validator
  -- ===================================================================
*************** SELECT srvname, usename FROM pgsql_fdw_c
*** 584,589 ****
--- 585,606 ----
  (0 rows)
  
  -- ===================================================================
+ -- statistics management
+ -- ===================================================================
+ DELETE FROM pg_statistic WHERE starelid = '"S 1"."T 1"'::regclass AND staattnum IN (1, 3);
+ SELECT pgsql_fdw_analyze('ft1');
+  pgsql_fdw_analyze 
+ -------------------
+                  5
+ (1 row)
+ 
+ SELECT count(*) FROM pg_statistic WHERE starelid = 'ft1'::regclass;
+  count 
+ -------
+      5
+ (1 row)
+ 
+ -- ===================================================================
  -- subtransaction
  -- ===================================================================
  BEGIN;
diff --git a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
index b0ea2b2..033cd6f 100644
*** a/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
--- b/contrib/pgsql_fdw/pgsql_fdw--1.0.sql
*************** SELECT c.srvid srvid,
*** 37,39 ****
--- 37,45 ----
             JOIN pg_catalog.pg_foreign_server s ON (s.oid = c.srvid);
  GRANT SELECT ON pgsql_fdw_connections TO public;
  
+ /* statistics management function */
+ CREATE FUNCTION pgsql_fdw_analyze(regclass)
+ RETURNS int
+ AS 'MODULE_PATHNAME'
+ LANGUAGE C;
+ 
diff --git a/contrib/pgsql_fdw/pgsql_fdw.c b/contrib/pgsql_fdw/pgsql_fdw.c
index 4916a45..06a3603 100644
*** a/contrib/pgsql_fdw/pgsql_fdw.c
--- b/contrib/pgsql_fdw/pgsql_fdw.c
***************
*** 13,32 ****
  #include "postgres.h"
  #include "fmgr.h"
  
  #include "catalog/pg_foreign_server.h"
  #include "catalog/pg_foreign_table.h"
  #include "commands/defrem.h"
  #include "commands/explain.h"
! #include "foreign/foreign.h"
  #include "funcapi.h"
  #include "miscadmin.h"
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.h"
  #include "optimizer/planmain.h"
  #include "optimizer/restrictinfo.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/rel.h"
  
  #include "pgsql_fdw.h"
  #include "connection.h"
--- 13,37 ----
  #include "postgres.h"
  #include "fmgr.h"
  
+ #include "access/transam.h"
  #include "catalog/pg_foreign_server.h"
  #include "catalog/pg_foreign_table.h"
  #include "commands/defrem.h"
  #include "commands/explain.h"
! #include "commands/vacuum.h"
  #include "funcapi.h"
  #include "miscadmin.h"
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.h"
  #include "optimizer/planmain.h"
  #include "optimizer/restrictinfo.h"
+ #include "parser/parse_type.h"
+ #include "utils/array.h"
+ #include "utils/builtins.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/rel.h"
+ #include "utils/syscache.h"
  
  #include "pgsql_fdw.h"
  #include "connection.h"
*************** typedef struct PgsqlFdwExecutionState
*** 125,130 ****
--- 130,137 ----
   */
  extern Datum pgsql_fdw_handler(PG_FUNCTION_ARGS);
  PG_FUNCTION_INFO_V1(pgsql_fdw_handler);
+ extern Datum pgsql_fdw_analyze(PG_FUNCTION_ARGS);
+ PG_FUNCTION_INFO_V1(pgsql_fdw_analyze);
  
  /*
   * FDW callback routines
*************** static void adjust_costs(double rows, in
*** 155,160 ****
--- 162,168 ----
  static void execute_query(ForeignScanState *node);
  static PGresult *fetch_result(ForeignScanState *node);
  static void store_result(ForeignScanState *node, PGresult *res);
+ static void store_remote_stats(PGresult *res, VacAttrStats *stats);
  
  /* Exported functions, but not written in pgsql_fdw.h. */
  void _PG_init(void);
*************** pgsql_fdw_handler(PG_FUNCTION_ARGS)
*** 211,216 ****
--- 219,229 ----
  /*
   * pgsqlGetForeignRelSize
   *		Estimate # of rows and width of the result of the scan
+  *
+  * Since we would have enough statistics about foreign data on local side by
+  * calling pgsql_fdw_analyze() for foreign table of pgsql_fdw, we can get good
+  * estimate of rows and width of this scan by calling
+  * set_baserel_size_estimates().
   */
  static void
  pgsqlGetForeignRelSize(PlannerInfo *root,
*************** store_result(ForeignScanState *node, PGr
*** 922,924 ****
--- 935,1523 ----
  	tuplestore_donestoring(festate->tuples);
  }
  
+ /*
+  * Update statistics of a foreign table managed by pgsql_fdw by copying remote
+  * statistics into local pg_statistic and pg_class.  If remote version is lower
+  * than 9.2, columns for slot 5 are ignored.
+  */ 
+ Datum
+ pgsql_fdw_analyze(PG_FUNCTION_ARGS)
+ {
+ 	Oid				relid = PG_GETARG_OID(0);
+ 	Relation		relation;
+ 	ListCell	   *lc;
+ 	int				nstats = 0;
+ 	MemoryContext	anl_context;
+ 	MemoryContext	caller_context;
+ 	const char	   *nspname;
+ 	const char	   *relname;
+ 	ForeignTable   *table;
+ 	ForeignServer  *server;
+ 	ForeignDataWrapper *wrapper;
+ 	FdwRoutine	   *routine;
+ 	UserMapping	   *user;
+ 	PGconn		   *conn;
+ 	PGresult	   *res = NULL;
+ 	StringInfoData	sql;
+ 	char		   *endp;
+ 	double			reltuples;
+ 	int				relpages;
+ 	int				attr_cnt;
+ 	int				tcnt;
+ 	int				i;
+ 	VacAttrStats  **vacattrstats;
+ 
+ 	/* Relation oid is required. */
+ 	if (PG_ARGISNULL(0))
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+ 				 errmsg("relation oid must not be NULL")));
+ 
+ 	/* Use short-lived expression context. */
+ 	anl_context = AllocSetContextCreate(CurrentMemoryContext,
+ 										"Analyze",
+ 										ALLOCSET_DEFAULT_MINSIZE,
+ 										ALLOCSET_DEFAULT_INITSIZE,
+ 										ALLOCSET_DEFAULT_MAXSIZE);
+ 	caller_context = MemoryContextSwitchTo(anl_context);
+ 
+ 	/*
+ 	 * Open the relation, getting ShareUpdateExclusiveLock to ensure that two
+ 	 * ANALYZE function don't run on it concurrently.  Of course, target must
+ 	 * be a foreign table of pgsql_fdw.
+ 	 */
+ 	relation = relation_open(relid, ShareUpdateExclusiveLock);
+ 	if (get_rel_relkind(relid) != RELKIND_FOREIGN_TABLE)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+ 				 errmsg("\"%s\" is not a foreign table",
+ 						RelationGetRelationName(relation))));
+ 
+ 	table = GetForeignTable(relid);
+ 	server = GetForeignServer(table->serverid);
+ 	wrapper = GetForeignDataWrapper(server->fdwid);
+ 	routine = GetFdwRoutine(wrapper->fdwhandler);
+ 	if (routine != &fdwroutine)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_FDW_TABLE_NOT_FOUND),
+ 				 errmsg("foreign table \"%s\" cannot handled by pgsql_fdw",
+ 						RelationGetRelationName(relation))));
+ 
+ 	/*
+ 	 * Establish connection against the foreign server to retrieve remote
+ 	 * statistics data.
+ 	 */
+ 	user = GetUserMapping(GetOuterUserId(), table->serverid);
+ 	conn = GetConnection(server, user, false);
+ 
+ 	/* Construct SQL statement to retrieve per-relation statistics. */
+ 	foreach(lc, table->options)
+ 	{
+ 		DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 		if (strcmp(def->defname, "nspname") == 0)
+ 			nspname = defGetString(def);
+ 		else if (strcmp(def->defname, "relname") == 0)
+ 			relname = defGetString(def);
+ 		
+ 	}
+ 	if (nspname == NULL)
+ 		nspname = get_namespace_name(get_rel_namespace(relid));
+ 	nspname = quote_identifier(nspname);
+ 	if (relname == NULL)
+ 		relname = get_rel_name(relid);
+ 	relname = quote_identifier(relname);
+ 
+ 	/*
+ 	 * Get per-relation statistics from remote pg_class.  We don't fetch
+ 	 * relallvisible, which is used for estimation about index-only scan,
+ 	 * because index-only scan is not available on foreign tables.
+ 	 * 
+ 	 * XXX Should we get summary of whole inherit-tree for inherited table?
+ 	 */
+ 	initStringInfo(&sql);
+ 	appendStringInfo(&sql,
+ 					 "SELECT relpages, "
+ 					 "       reltuples "
+ 					 "  FROM pg_catalog.pg_class "
+ 					 " WHERE oid = '%s.%s'::regclass",
+ 					 nspname, relname);
+ 
+ 	PG_TRY();
+ 	{
+ 		res = PQexec(conn, sql.data);
+ 
+ 		if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 			ereport(ERROR,
+ 					(errmsg("could not get per-table statistics"),
+ 					 errdetail("%s", PQerrorMessage(conn))));
+ 		if (PQntuples(res) != 1)
+ 			ereport(ERROR,
+ 					(errmsg("invalid number of tuples: %d", PQntuples(res))));
+ 
+ 		relpages = strtol(PGRES_VAL0(0), &endp, 10);
+ 		if (*endp != '\0')
+ 			ereport(ERROR,
+ 					(errmsg("invalid format for relpages: %s", PGRES_VAL0(0))));
+ 		reltuples = strtod(PGRES_VAL0(1), &endp);
+ 		if (*endp != '\0')
+ 			ereport(ERROR,
+ 					(errmsg("invalid format for reltuples: %s", PGRES_VAL0(1))));
+ 		PQclear(res);
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		PQclear(res);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	/*
+ 	 * Get per-column statistics from remote pg_statistic.  Note that some of
+ 	 * local columns might be dropped.
+ 	 *
+ 	 * FIXME When porting this routine as ANALYZE handler, we need to care
+ 	 * vacstmt->va_cols here.
+ 	 *
+ 	 */
+ #ifdef NOT_USED
+ 	if (va_cols != NIL)
+ 	{
+ 		ListCell   *le;
+ 
+ 		vacattrstats = (VacAttrStats **) palloc(list_length(va_cols) *
+ 												sizeof(VacAttrStats *));
+ 		tcnt = 0;
+ 		foreach(le, va_cols)
+ 		{
+ 			char	   *col = strVal(lfirst(le));
+ 
+ 			i = attnameAttNum(relation, col, false);
+ 			if (i == InvalidAttrNumber)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_UNDEFINED_COLUMN),
+ 					errmsg("column \"%s\" of relation \"%s\" does not exist",
+ 						   col, RelationGetRelationName(relation))));
+ 			vacattrstats[tcnt] = examine_attribute(relation, i, NULL);
+ 			if (vacattrstats[tcnt] != NULL)
+ 				tcnt++;
+ 		}
+ 		attr_cnt = tcnt;
+ 	}
+ 	else
+ #endif
+ 	{
+ 		attr_cnt = relation->rd_att->natts;
+ 		vacattrstats = (VacAttrStats **)
+ 			palloc(attr_cnt * sizeof(VacAttrStats *));
+ 		tcnt = 0;
+ 		for (i = 1; i <= attr_cnt; i++)
+ 		{
+ 			vacattrstats[tcnt] = examine_attribute(relation, i, NULL);
+ 			if (vacattrstats[tcnt] != NULL)
+ 				tcnt++;
+ 		}
+ 		attr_cnt = tcnt;
+ 	}
+ 
+ 	/* Retrieve statistics for each requested column from foreign server. */
+ 	for (i = 0; i < attr_cnt; i++)
+ 	{
+ 		List		   *options;
+ 		ListCell	   *lc;
+ 		const char	   *colname = NULL;
+ 		StringInfoData	sql_stat;
+ 
+ 		/* Use colname FDW option to determine remote attribute, if any. */
+ 		options = GetForeignColumnOptions(relid,
+ 										  vacattrstats[i]->attr->attnum);
+ 		foreach(lc, options)
+ 		{
+ 			DefElem	   *def = (DefElem *) lfirst(lc);
+ 
+ 			if (strcmp(def->defname, "colname") == 0)
+ 			{
+ 				colname = defGetString(def);
+ 				break;
+ 			}
+ 		}
+ 		if (colname == NULL)
+ 			colname = get_attname(relation->rd_id,
+ 								  vacattrstats[i]->attr->attnum);
+ 
+ 		/* No need to quote column name here. */
+ 		initStringInfo(&sql_stat);
+ 		if (PQserverVersion(conn) >= 90200)
+ 		{
+ 			appendStringInfo(&sql_stat,
+ 							 "SELECT starelid,"
+ 							 "       staattnum,"
+ 							 /* fixed value is used for stainherit, see below */
+ 							 "       stanullfrac,"
+ 							 "       stawidth,"
+ 							 "       stadistinct,"
+ 							 "       stakind1,"
+ 							 "       stakind2,"
+ 							 "       stakind3,"
+ 							 "       stakind4,"
+ 							 "       stakind5,"
+ 							 "       staop1,"
+ 							 "       staop2,"
+ 							 "       staop3,"
+ 							 "       staop4,"
+ 							 "       staop5,"
+ 							 "       stanumbers1,"
+ 							 "       stanumbers2,"
+ 							 "       stanumbers3,"
+ 							 "       stanumbers4,"
+ 							 "       stanumbers5,"
+ 							 "       stavalues1,"
+ 							 "       stavalues2,"
+ 							 "       stavalues3,"
+ 							 "       stavalues4,"
+ 							 "       stavalues5"
+ 							 "  FROM pg_catalog.pg_statistic "
+ 							 " WHERE starelid = '%s.%s'::regclass "
+ 							 "   AND staattnum = ("
+ 							 "           SELECT attnum "
+ 							 "             FROM pg_catalog.pg_attribute "
+ 							 "            WHERE attrelid = '%s.%s'::regclass "
+ 							 "              AND attname = '%s')",
+ 							 nspname, relname, nspname, relname, colname);
+ 		}
+ 		else
+ 		{
+ 			appendStringInfo(&sql_stat,
+ 							 "SELECT starelid,"
+ 							 "       staattnum,"
+ 							 /* fixed value is used for stainherit, see below */
+ 							 "       stanullfrac,"
+ 							 "       stawidth,"
+ 							 "       stadistinct,"
+ 							 "       stakind1,"
+ 							 "       stakind2,"
+ 							 "       stakind3,"
+ 							 "       stakind4,"
+ 							 "       staop1,"
+ 							 "       staop2,"
+ 							 "       staop3,"
+ 							 "       staop4,"
+ 							 "       stanumbers1,"
+ 							 "       stanumbers2,"
+ 							 "       stanumbers3,"
+ 							 "       stanumbers4,"
+ 							 "       stavalues1,"
+ 							 "       stavalues2,"
+ 							 "       stavalues3,"
+ 							 "       stavalues4"
+ 							 "  FROM pg_catalog.pg_statistic "
+ 							 " WHERE starelid = '%s.%s'::regclass "
+ 							 "   AND staattnum = ("
+ 							 "           SELECT attnum "
+ 							 "             FROM pg_catalog.pg_attribute "
+ 							 "            WHERE attrelid = '%s.%s'::regclass "
+ 							 "              AND attname = '%s')",
+ 							 nspname, relname, nspname, relname, colname);
+ 		}
+ 
+ 		/*
+ 		 * If foreign server is PG 9.0 or later, inherited tables might have
+ 		 * two sets of statistics; one contains information about the table
+ 		 * itself, and another contains information about whole inherit-tree
+ 		 * topped by the table.
+ 		 *
+ 		 * We prefer statistics of whole inherit-tree if any, because parent
+ 		 * table returns contents of descendants too.  However, we overwrite
+ 		 * stainherit by "false" for local statistics, because foreign tables
+ 		 * can't be parent table.
+ 		 */
+ 		if (PQserverVersion(conn) >= 90000)
+ 			appendStringInfo(&sql_stat, "ORDER BY stainherit DESC LIMIT 1");
+ 
+ 		res = NULL;
+ 		PG_TRY();
+ 		{
+ 			res = PQexec(conn, sql_stat.data);
+ 			pfree(sql_stat.data);
+ 			if (PQresultStatus(res) != PGRES_TUPLES_OK)
+ 				ereport(ERROR,
+ 						(errmsg("could not get per-column statistics"),
+ 						 errdetail("%s", PQerrorMessage(conn))));
+ 
+ 			/* If remote table doesn't have any statistic, skip this column. */
+ 			if (PQntuples(res) > 0)
+ 			{
+ 				store_remote_stats(res, vacattrstats[i]);
+ 				nstats++;
+ 			}
+ 
+ 			PQclear(res);
+ 		}
+ 		PG_CATCH();
+ 		{
+ 			PQclear(res);
+ 			PG_RE_THROW();
+ 		}
+ 		PG_END_TRY();
+ 	}
+ 
+ 	/* Disconnect from foreign server. */
+ 	ReleaseConnection(conn);
+ 
+ 	/* Update local pg_statistic with retrieved statistics. */
+ 	vac_update_attstats(RelationGetRelid(relation),
+ 						false,
+ 						attr_cnt,
+ 						vacattrstats);
+ 
+ 	/*
+ 	 * Update local pg_class with retrieved statistics.  We set relallvisible
+ 	 * to 0 always.
+ 	 */
+ 	vac_update_relstats(relation,
+ 						relpages,
+ 						reltuples,
+ 						0,
+ 						false,
+ 						InvalidTransactionId);
+ 
+ 	/* Restore memory context. */
+ 	MemoryContextSwitchTo(caller_context);
+ 	MemoryContextDelete(anl_context);
+ 
+ #ifdef NOT_USED
+ 	/* Print verbose messages. */
+ 	if (vacstmt->options & VACOPT_VERBOSE)
+ 		elog(INFO, "%s: relpages=%d, reltuples=%f, %d per-column stats copied",
+ 			 vacstmt->relation->relname,
+ 			 relpages,
+ 			 reltuples,
+ 			 nstats);
+ #endif
+ 
+ 	/* Close the relation with releasing the lock. */
+ 	relation_close(relation, ShareUpdateExclusiveLock);
+ 
+ 	PG_RETURN_INT32(nstats);
+ }
+ 
+ /*
+  * Read text representation of remote statistics from res and store them into
+  * stats with conversion to internal representation.
+  */
+ static void
+ store_remote_stats(PGresult *res, VacAttrStats *stats)
+ {
+ 	Type			float4array_type;
+ 	Type			textarray_type;
+ 	Oid				elemtypeid;
+ 	Type			elemtype;
+ 	Oid				in_func_oid;
+ 	Form_pg_type	attrtype;
+ 	Oid				typeioparam;
+ 	FmgrInfo		in_function;
+ 
+ 	int				i_stanullfrac;
+ 	int				i_stawidth;
+ 	int				i_stadistinct;
+ 	int				i_stakind[STATISTIC_NUM_SLOTS];
+ 	int				i_staop[STATISTIC_NUM_SLOTS];
+ 	int				i_stanumbers[STATISTIC_NUM_SLOTS];
+ 	int				i_stavalues[STATISTIC_NUM_SLOTS];
+ 	int				i;
+ 
+ 	/* Get information of actual type of array element. */
+ 	elemtypeid = stats->attr->atttypid;
+ 	elemtype = typeidType(elemtypeid);
+ 	getTypeInputInfo(elemtypeid, &in_func_oid, &typeioparam);
+ 	fmgr_info(in_func_oid, &in_function);
+ 
+ 	attrtype = (Form_pg_type) palloc(sizeof(FormData_pg_type));
+ 	memcpy(attrtype, GETSTRUCT(elemtype), sizeof(FormData_pg_type));
+ 
+ 	i_stanullfrac = PQfnumber(res, "stanullfrac");
+ 	i_stawidth = PQfnumber(res, "stawidth");
+ 	i_stadistinct = PQfnumber(res, "stadistinct");
+ 	i_stakind[0] = PQfnumber(res, "stakind1");
+ 	i_stakind[1] = PQfnumber(res, "stakind2");
+ 	i_stakind[2] = PQfnumber(res, "stakind3");
+ 	i_stakind[3] = PQfnumber(res, "stakind4");
+ 	i_stakind[4] = PQfnumber(res, "stakind5");
+ 	i_staop[0] = PQfnumber(res, "staop1");
+ 	i_staop[1] = PQfnumber(res, "staop2");
+ 	i_staop[2] = PQfnumber(res, "staop3");
+ 	i_staop[3] = PQfnumber(res, "staop4");
+ 	i_staop[4] = PQfnumber(res, "staop5");
+ 	i_stanumbers[0] = PQfnumber(res, "stanumbers1");
+ 	i_stanumbers[1] = PQfnumber(res, "stanumbers2");
+ 	i_stanumbers[2] = PQfnumber(res, "stanumbers3");
+ 	i_stanumbers[3] = PQfnumber(res, "stanumbers4");
+ 	i_stanumbers[4] = PQfnumber(res, "stanumbers5");
+ 	i_stavalues[0] = PQfnumber(res, "stavalues1");
+ 	i_stavalues[1] = PQfnumber(res, "stavalues2");
+ 	i_stavalues[2] = PQfnumber(res, "stavalues3");
+ 	i_stavalues[3] = PQfnumber(res, "stavalues4");
+ 	i_stavalues[4] = PQfnumber(res, "stavalues5");
+ 
+ 	/*
+ 	 * If statistics are found, mark this column to be updated later
+ 	 * and fill with retrieved remote statistics.
+ 	 *
+ 	 * For scalar values, just copying values is enough, but we have to
+ 	 * be conscious the types of elements for array values.  libpq
+ 	 * gives us an array value in a string representation, such as
+ 	 * "{foo, bar}", so we need to (1)separate an array string into
+ 	 * elements, (2)convert each element into Datum representation, and
+ 	 * (3) create a Datum representation of array from Datum elements.
+ 	 *
+ 	 * Note: OID of operator (staopN) MUST match between remote and local.
+ 	 */
+ 	stats->stats_valid = true;
+ 	stats->stanullfrac = strtof(PGRES_VAL0(i_stanullfrac), NULL);
+ 	stats->stawidth = strtol(PGRES_VAL0(i_stawidth), NULL, 10);
+ 	stats->stadistinct = strtof(PGRES_VAL0(i_stadistinct), NULL);
+ 
+ 	/*
+ 	 * Get type information for stanumbers and stavalues.  We assume stavalues
+ 	 * as array of text during extracting elements, and then extracted
+ 	 * elements are treated as the type of foreign table attributes.
+ 	 */
+ 	float4array_type = typeidType(FLOAT4ARRAYOID);
+ 	textarray_type = typeidType(TEXTARRAYOID);
+ 
+ 	for (i = 0; i < STATISTIC_NUM_SLOTS; i++)
+ 	{
+ 		int			atttypmod = 0;
+ 		int			j;
+ 		Datum		tnumbers = 0;
+ 		ArrayType  *array;
+ 		int			nitems;
+ 		bits8	   *bitmap;
+ 		int			bitmask;
+ 		char	   *p;
+ 
+ 		/* PostgreSQL 9.1 and older don't have stakind5. */
+ 		if (i_stakind[i] < 0 || i_staop[i] < 0 ||
+ 			i_stanumbers[i] < 0 || i_stavalues[i] < 0)
+ 			continue;
+ 
+ 		stats->stakind[i] = strtol(PGRES_VAL0(i_stakind[i]), NULL, 10);
+ 		stats->staop[i] = strtol(PGRES_VAL0(i_staop[i]), NULL, 10);
+ 
+ 		/*
+ 		 * Extract element values of stanumbersN from text representation of
+ 		 * array, if any.
+ 		 */
+ 		if (!PGRES_NULL0(i_stanumbers[i]))
+ 		{
+ 			/* Separate array string into each float4 elements. */
+ 			tnumbers = stringTypeDatum(float4array_type,
+ 									   PGRES_VAL0(i_stanumbers[i]),
+ 									   -1);
+ 			array = DatumGetArrayTypeP(tnumbers);
+ 			nitems = ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array));
+ 
+ 			bitmap = ARR_NULLBITMAP(array);
+ 			bitmask = 1;
+ 
+ 			stats->numnumbers[i] = nitems;
+ 			stats->stanumbers[i] = (float4 *) palloc(nitems * sizeof(float4));
+ 			for (j = 0; j < nitems; j++)
+ 			{
+ 				p = ARR_DATA_PTR(array);
+ 
+ 				if (bitmap && (*bitmap & bitmask) == 0)
+ 				{
+ 					/* nulls can be ignored */
+ 				}
+ 				else
+ 				{
+ 					stats->stanumbers[i][j] = * (float4 *) ARR_DATA_PTR(array);
+ 					p = p + sizeof(float4);
+ 					p = (char *) att_align_nominal(p, 'i');
+ 				}
+ 
+ 				/* advance bitmap pointer if any */
+ 				if (bitmap)
+ 				{
+ 					bitmask <<= 1;
+ 					if (bitmask == 0x100)
+ 					{
+ 						bitmap++;
+ 						bitmask = 1;
+ 					}
+ 				}
+ 			}
+ 		}
+ 		else
+ 		{
+ 			stats->numnumbers[i] = 0;
+ 			stats->stanumbers[i] = NULL;
+ 		}
+ 
+ 		/*
+ 		 * Extract element values of stavaluesN from text representation of
+ 		 * array, if any.
+ 		 */
+ 		if (!PGRES_NULL0(i_stavalues[i]))
+ 		{
+ 			/*
+ 			 * Separate array string into each elements string, and convert
+ 			 * each element to actual column data type.
+ 			 */
+ 			tnumbers = stringTypeDatum(textarray_type,
+ 									   PGRES_VAL0(i_stavalues[i]),
+ 									   -1);
+ 			array = DatumGetArrayTypeP(tnumbers);
+ 			nitems = ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array));
+ 
+ 			bitmap = ARR_NULLBITMAP(array);
+ 			bitmask = 1;
+ 			p = ARR_DATA_PTR(array);
+ 
+ 			stats->numvalues[i] = nitems;
+ 			stats->stavalues[i] = (Datum *) palloc(nitems * sizeof(Datum));
+ 
+ 			for (j = 0; j < nitems; j++)
+ 			{
+ 				char	   *string;
+ 
+ 				if (bitmap && (*bitmap & bitmask) == 0)
+ 				{
+ 					/* nulls can be ignored */
+ 				}
+ 				else
+ 				{
+ 					string = text_to_cstring((text *) p);
+ 					stats->stavalues[i][j] = InputFunctionCall(&in_function,
+ 															   string,
+ 															   typeioparam,
+ 															   atttypmod);
+ 					p = p + VARSIZE_ANY(p);
+ 					p = (char *) att_align_nominal(p, 'i');
+ 				}
+ 
+ 				/* advance bitmap pointer if any */
+ 				if (bitmap)
+ 				{
+ 					bitmask <<= 1;
+ 					if (bitmask == 0x100)
+ 					{
+ 						bitmap++;
+ 						bitmask = 1;
+ 					}
+ 				}
+ 			}
+ 		}
+ 		else
+ 		{
+ 			stats->numvalues[i] = 0;
+ 			stats->stavalues[i] = NULL;
+ 		}
+ 	}
+ 
+ 	/* Clean up */
+ 	ReleaseSysCache(elemtype);
+ 	ReleaseSysCache(textarray_type);
+ 	ReleaseSysCache(float4array_type);
+ }
diff --git a/contrib/pgsql_fdw/sql/pgsql_fdw.sql b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
index b7cd71d..eef1cfa 100644
*** a/contrib/pgsql_fdw/sql/pgsql_fdw.sql
--- b/contrib/pgsql_fdw/sql/pgsql_fdw.sql
*************** INSERT INTO "S 1"."T 2"
*** 85,90 ****
--- 85,91 ----
  	       'AAA' || to_char(id, 'FM000')
  	FROM generate_series(1, 100) id;
  COMMIT;
+ ANALYZE "S 1"."T 1";
  
  -- ===================================================================
  -- tests for pgsql_fdw_validator
*************** SELECT pgsql_fdw_disconnect(srvid, usesy
*** 235,240 ****
--- 236,248 ----
  SELECT srvname, usename FROM pgsql_fdw_connections;
  
  -- ===================================================================
+ -- statistics management
+ -- ===================================================================
+ DELETE FROM pg_statistic WHERE starelid = '"S 1"."T 1"'::regclass AND staattnum IN (1, 3);
+ SELECT pgsql_fdw_analyze('ft1');
+ SELECT count(*) FROM pg_statistic WHERE starelid = 'ft1'::regclass;
+ 
+ -- ===================================================================
  -- subtransaction
  -- ===================================================================
  BEGIN;
diff --git a/doc/src/sgml/pgsql-fdw.sgml b/doc/src/sgml/pgsql-fdw.sgml
index eb69f01..2c16c43 100644
*** a/doc/src/sgml/pgsql-fdw.sgml
--- b/doc/src/sgml/pgsql-fdw.sgml
*************** postgres=# SELECT pgsql_fdw_disconnect(s
*** 218,223 ****
--- 218,244 ----
   </sect2>
  
   <sect2>
+   <title>Statistics Management</title>
+   <para>
+    <application>pgsql_fdw</application> provides a function
+    <function>pgsql_fdw_analyze()</function> which updates local statistics
+    stored in <structname>pg_statistic</structname> and
+    <structname>pg_class</structname> by copying remote statistics.  This
+    function takes a regclass argument of target foreign table, and returns
+    number of attributes of which per-attribute statistics are updated.  Thus,
+    this function may return number less than attribute count when remote table
+    doesn't have statistics for all attributes.
+   </para>
+   <note>
+    <para>
+     Number of statistics slots in <structname>pg_statistic</structname> is
+     increased to 5 in 9.2, so this function copies only slot 1 to 4 from older
+     versions. 
+    </para>
+   </note>
+  </sect2>
+ 
+  <sect2>
    <title>Estimation of Costs and Rows</title>
    <para>
     The <application>pgsql_fdw</application> estimates the costs of a foreign
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 9cd6e67..21b1bf1 100644
*** a/src/backend/commands/analyze.c
--- b/src/backend/commands/analyze.c
*************** static void compute_index_stats(Relation
*** 94,101 ****
  					AnlIndexData *indexdata, int nindexes,
  					HeapTuple *rows, int numrows,
  					MemoryContext col_context);
- static VacAttrStats *examine_attribute(Relation onerel, int attnum,
- 				  Node *index_expr);
  static int acquire_sample_rows(Relation onerel, HeapTuple *rows,
  					int targrows, double *totalrows, double *totaldeadrows);
  static double random_fract(void);
--- 94,99 ----
*************** static int	compare_rows(const void *a, c
*** 105,112 ****
  static int acquire_inherited_sample_rows(Relation onerel,
  							  HeapTuple *rows, int targrows,
  							  double *totalrows, double *totaldeadrows);
- static void update_attstats(Oid relid, bool inh,
- 				int natts, VacAttrStats **vacattrstats);
  static Datum std_fetch_func(VacAttrStatsP stats, int rownum, bool *isNull);
  static Datum ind_fetch_func(VacAttrStatsP stats, int rownum, bool *isNull);
  
--- 103,108 ----
*************** analyze_rel(Oid relid, VacuumStmt *vacst
*** 209,215 ****
  	}
  
  	/*
! 	 * We can ANALYZE any table except pg_statistic. See update_attstats
  	 */
  	if (RelationGetRelid(onerel) == StatisticRelationId)
  	{
--- 205,211 ----
  	}
  
  	/*
! 	 * We can ANALYZE any table except pg_statistic. See vac_update_attstats
  	 */
  	if (RelationGetRelid(onerel) == StatisticRelationId)
  	{
*************** analyze_rel(Oid relid, VacuumStmt *vacst
*** 239,245 ****
  	 * Close source relation now, but keep lock so that no one deletes it
  	 * before we commit.  (If someone did, they'd fail to clean up the entries
  	 * we made in pg_statistic.  Also, releasing the lock before commit would
! 	 * expose us to concurrent-update failures in update_attstats.)
  	 */
  	relation_close(onerel, NoLock);
  
--- 235,241 ----
  	 * Close source relation now, but keep lock so that no one deletes it
  	 * before we commit.  (If someone did, they'd fail to clean up the entries
  	 * we made in pg_statistic.  Also, releasing the lock before commit would
! 	 * expose us to concurrent-update failures in vac_update_attstats.)
  	 */
  	relation_close(onerel, NoLock);
  
*************** do_analyze_rel(Relation onerel, VacuumSt
*** 514,528 ****
  		 * previous statistics for the target columns.	(If there are stats in
  		 * pg_statistic for columns we didn't process, we leave them alone.)
  		 */
! 		update_attstats(RelationGetRelid(onerel), inh,
! 						attr_cnt, vacattrstats);
  
  		for (ind = 0; ind < nindexes; ind++)
  		{
  			AnlIndexData *thisdata = &indexdata[ind];
  
! 			update_attstats(RelationGetRelid(Irel[ind]), false,
! 							thisdata->attr_cnt, thisdata->vacattrstats);
  		}
  	}
  
--- 510,524 ----
  		 * previous statistics for the target columns.	(If there are stats in
  		 * pg_statistic for columns we didn't process, we leave them alone.)
  		 */
! 		vac_update_attstats(RelationGetRelid(onerel), inh,
! 							attr_cnt, vacattrstats);
  
  		for (ind = 0; ind < nindexes; ind++)
  		{
  			AnlIndexData *thisdata = &indexdata[ind];
  
! 			vac_update_attstats(RelationGetRelid(Irel[ind]), false,
! 								thisdata->attr_cnt, thisdata->vacattrstats);
  		}
  	}
  
*************** compute_index_stats(Relation onerel, dou
*** 805,811 ****
   * If index_expr isn't NULL, then we're trying to analyze an expression index,
   * and index_expr is the expression tree representing the column's data.
   */
! static VacAttrStats *
  examine_attribute(Relation onerel, int attnum, Node *index_expr)
  {
  	Form_pg_attribute attr = onerel->rd_att->attrs[attnum - 1];
--- 801,807 ----
   * If index_expr isn't NULL, then we're trying to analyze an expression index,
   * and index_expr is the expression tree representing the column's data.
   */
! VacAttrStats *
  examine_attribute(Relation onerel, int attnum, Node *index_expr)
  {
  	Form_pg_attribute attr = onerel->rd_att->attrs[attnum - 1];
*************** acquire_inherited_sample_rows(Relation o
*** 1538,1544 ****
  
  
  /*
!  *	update_attstats() -- update attribute statistics for one relation
   *
   *		Statistics are stored in several places: the pg_class row for the
   *		relation has stats about the whole relation, and there is a
--- 1534,1540 ----
  
  
  /*
!  *	vac_update_attstats() -- update attribute statistics for one relation
   *
   *		Statistics are stored in several places: the pg_class row for the
   *		relation has stats about the whole relation, and there is a
*************** acquire_inherited_sample_rows(Relation o
*** 1559,1566 ****
   *		ANALYZE the same table concurrently.  Presently, we lock that out
   *		by taking a self-exclusive lock on the relation in analyze_rel().
   */
! static void
! update_attstats(Oid relid, bool inh, int natts, VacAttrStats **vacattrstats)
  {
  	Relation	sd;
  	int			attno;
--- 1555,1562 ----
   *		ANALYZE the same table concurrently.  Presently, we lock that out
   *		by taking a self-exclusive lock on the relation in analyze_rel().
   */
! void
! vac_update_attstats(Oid relid, bool inh, int natts, VacAttrStats **vacattrstats)
  {
  	Relation	sd;
  	int			attno;
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 3deee66..da9bf8a 100644
*** a/src/include/commands/vacuum.h
--- b/src/include/commands/vacuum.h
*************** extern void vac_update_relstats(Relation
*** 154,159 ****
--- 154,161 ----
  					BlockNumber num_all_visible_pages,
  					bool hasindex,
  					TransactionId frozenxid);
+ extern void vac_update_attstats(Oid relid, bool inh,
+ 					int natts, VacAttrStats **vacattrstats);
  extern void vacuum_set_xid_limits(int freeze_min_age, int freeze_table_age,
  					  bool sharedRel,
  					  TransactionId *oldestXmin,
*************** extern void lazy_vacuum_rel(Relation one
*** 170,174 ****
--- 172,178 ----
  extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
  			BufferAccessStrategy bstrategy);
  extern bool std_typanalyze(VacAttrStats *stats);
+ extern VacAttrStats *examine_attribute(Relation onerel, int attnum,
+ 			Node *index_expr);
  
  #endif   /* VACUUM_H */