SQL access to database attributes

*** a/contrib/sepgsql/expected/alter.out
--- b/contrib/sepgsql/expected/alter.out
***************
*** 110,116 **** SET search_path = regtest_schema, regtest_schema_2, public;
  --
  -- misc ALTER commands
  --
! ALTER DATABASE regtest_sepgsql_test_database CONNECTION LIMIT 999;
  LOG:  SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:unconfined_t:s0 tcontext=unconfined_u:object_r:sepgsql_db_t:s0 tclass=db_database name="regtest_sepgsql_test_database"
  ALTER DATABASE regtest_sepgsql_test_database SET search_path TO regtest_schema, public; -- not supported yet
  ALTER TABLE regtest_table ADD COLUMN d float;
--- 110,116 ----
  --
  -- misc ALTER commands
  --
! ALTER DATABASE regtest_sepgsql_test_database CONNECTION_LIMIT 999;
  LOG:  SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:unconfined_t:s0 tcontext=unconfined_u:object_r:sepgsql_db_t:s0 tclass=db_database name="regtest_sepgsql_test_database"
  ALTER DATABASE regtest_sepgsql_test_database SET search_path TO regtest_schema, public; -- not supported yet
  ALTER TABLE regtest_table ADD COLUMN d float;
*** a/contrib/sepgsql/sql/alter.sql
--- b/contrib/sepgsql/sql/alter.sql
***************
*** 85,91 **** SET search_path = regtest_schema, regtest_schema_2, public;
  --
  -- misc ALTER commands
  --
! ALTER DATABASE regtest_sepgsql_test_database CONNECTION LIMIT 999;
  ALTER DATABASE regtest_sepgsql_test_database SET search_path TO regtest_schema, public; -- not supported yet
  
  ALTER TABLE regtest_table ADD COLUMN d float;
--- 85,91 ----
  --
  -- misc ALTER commands
  --
! ALTER DATABASE regtest_sepgsql_test_database CONNECTION_LIMIT 999;
  ALTER DATABASE regtest_sepgsql_test_database SET search_path TO regtest_schema, public; -- not supported yet
  
  ALTER TABLE regtest_table ADD COLUMN d float;
*** a/doc/src/sgml/ref/alter_database.sgml
--- b/doc/src/sgml/ref/alter_database.sgml
***************
*** 25,31 **** ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> [ [ WITH ] <rep
  
  <phrase>where <replaceable class="PARAMETER">option</replaceable> can be:</phrase>
  
!     CONNECTION LIMIT <replaceable class="PARAMETER">connlimit</replaceable>
  
  ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable>new_name</replaceable>
  
--- 25,31 ----
  
  <phrase>where <replaceable class="PARAMETER">option</replaceable> can be:</phrase>
  
!     CONNECTION_LIMIT <replaceable class="PARAMETER">connection_limit</replaceable>
  
  ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable>new_name</replaceable>
  
***************
*** 107,113 **** ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RESET ALL
       </varlistentry>
  
       <varlistentry>
!       <term><replaceable class="parameter">connlimit</replaceable></term>
        <listitem>
         <para>
          How many concurrent connections can be made
--- 107,113 ----
       </varlistentry>
  
       <varlistentry>
!       <term><replaceable class="parameter">connection_limit</replaceable></term>
        <listitem>
         <para>
          How many concurrent connections can be made
*** a/doc/src/sgml/ref/create_database.sgml
--- b/doc/src/sgml/ref/create_database.sgml
***************
*** 28,34 **** CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
             [ LC_COLLATE [=] <replaceable class="parameter">lc_collate</replaceable> ]
             [ LC_CTYPE [=] <replaceable class="parameter">lc_ctype</replaceable> ]
             [ TABLESPACE [=] <replaceable class="parameter">tablespace_name</replaceable> ]
!            [ CONNECTION LIMIT [=] <replaceable class="parameter">connlimit</replaceable> ] ]
  </synopsis>
   </refsynopsisdiv>
  
--- 28,34 ----
             [ LC_COLLATE [=] <replaceable class="parameter">lc_collate</replaceable> ]
             [ LC_CTYPE [=] <replaceable class="parameter">lc_ctype</replaceable> ]
             [ TABLESPACE [=] <replaceable class="parameter">tablespace_name</replaceable> ]
!            [ CONNECTION_LIMIT [=] <replaceable class="parameter">connection_limit</replaceable> ] ]
  </synopsis>
   </refsynopsisdiv>
  
***************
*** 148,154 **** CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
       </varlistentry>
  
       <varlistentry>
!       <term><replaceable class="parameter">connlimit</replaceable></term>
        <listitem>
         <para>
          How many concurrent connections can be made
--- 148,154 ----
       </varlistentry>
  
       <varlistentry>
!       <term><replaceable class="parameter">connection_limit</replaceable></term>
        <listitem>
         <para>
          How many concurrent connections can be made
***************
*** 231,237 **** CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
    </para>
  
    <para>
!    The <literal>CONNECTION LIMIT</> option is only enforced approximately;
     if two new sessions start at about the same time when just one
     connection <quote>slot</> remains for the database, it is possible that
     both will fail.  Also, the limit is not enforced against superusers.
--- 231,237 ----
    </para>
  
    <para>
!    The <literal>CONNECTION_LIMIT</> option is only enforced approximately;
     if two new sessions start at about the same time when just one
     connection <quote>slot</> remains for the database, it is possible that
     both will fail.  Also, the limit is not enforced against superusers.
*** a/src/backend/commands/dbcommands.c
--- b/src/backend/commands/dbcommands.c
***************
*** 39,44 ****
--- 39,45 ----
  #include "catalog/pg_tablespace.h"
  #include "commands/comment.h"
  #include "commands/dbcommands.h"
+ #include "commands/defrem.h"
  #include "commands/seclabel.h"
  #include "commands/tablespace.h"
  #include "mb/pg_wchar.h"
***************
*** 188,194 **** createdb(const CreatedbStmt *stmt)
  						 errmsg("conflicting or redundant options")));
  			dctype = defel;
  		}
! 		else if (strcmp(defel->defname, "connectionlimit") == 0)
  		{
  			if (dconnlimit)
  				ereport(ERROR,
--- 189,195 ----
  						 errmsg("conflicting or redundant options")));
  			dctype = defel;
  		}
! 		else if (strcmp(defel->defname, "connection_limit") == 0)
  		{
  			if (dconnlimit)
  				ereport(ERROR,
***************
*** 204,224 **** createdb(const CreatedbStmt *stmt)
  					 errhint("Consider using tablespaces instead.")));
  		}
  		else
! 			elog(ERROR, "option \"%s\" not recognized",
! 				 defel->defname);
  	}
  
! 	if (downer && downer->arg)
! 		dbowner = strVal(downer->arg);
! 	if (dtemplate && dtemplate->arg)
! 		dbtemplate = strVal(dtemplate->arg);
! 	if (dencoding && dencoding->arg)
  	{
  		const char *encoding_name;
  
  		if (IsA(dencoding->arg, Integer))
  		{
! 			encoding = intVal(dencoding->arg);
  			encoding_name = pg_encoding_to_char(encoding);
  			if (strcmp(encoding_name, "") == 0 ||
  				pg_valid_server_encoding(encoding_name) < 0)
--- 205,226 ----
  					 errhint("Consider using tablespaces instead.")));
  		}
  		else
! 			ereport(ERROR,
! 					(errcode(ERRCODE_SYNTAX_ERROR),
! 					 errmsg("option \"%s\" not recognized", defel->defname)));
  	}
  
! 	if (downer)
! 		dbowner = defGetString(downer);
! 	if (dtemplate)
! 		dbtemplate = defGetString(dtemplate);
! 	if (dencoding)
  	{
  		const char *encoding_name;
  
  		if (IsA(dencoding->arg, Integer))
  		{
! 			encoding = defGetInt32(dencoding);
  			encoding_name = pg_encoding_to_char(encoding);
  			if (strcmp(encoding_name, "") == 0 ||
  				pg_valid_server_encoding(encoding_name) < 0)
***************
*** 229,235 **** createdb(const CreatedbStmt *stmt)
  		}
  		else if (IsA(dencoding->arg, String))
  		{
! 			encoding_name = strVal(dencoding->arg);
  			encoding = pg_valid_server_encoding(encoding_name);
  			if (encoding < 0)
  				ereport(ERROR,
--- 231,237 ----
  		}
  		else if (IsA(dencoding->arg, String))
  		{
! 			encoding_name = defGetString(dencoding);
  			encoding = pg_valid_server_encoding(encoding_name);
  			if (encoding < 0)
  				ereport(ERROR,
***************
*** 241,254 **** createdb(const CreatedbStmt *stmt)
  			elog(ERROR, "unrecognized node type: %d",
  				 nodeTag(dencoding->arg));
  	}
! 	if (dcollate && dcollate->arg)
! 		dbcollate = strVal(dcollate->arg);
! 	if (dctype && dctype->arg)
! 		dbctype = strVal(dctype->arg);
  
! 	if (dconnlimit && dconnlimit->arg)
  	{
! 		dbconnlimit = intVal(dconnlimit->arg);
  		if (dbconnlimit < -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
--- 243,256 ----
  			elog(ERROR, "unrecognized node type: %d",
  				 nodeTag(dencoding->arg));
  	}
! 	if (dcollate)
! 		dbcollate = defGetString(dcollate);
! 	if (dctype)
! 		dbctype = defGetString(dctype);
  
! 	if (dconnlimit)
  	{
! 		dbconnlimit = defGetInt32(dconnlimit);
  		if (dbconnlimit < -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
***************
*** 1341,1347 **** AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
  	{
  		DefElem    *defel = (DefElem *) lfirst(option);
  
! 		if (strcmp(defel->defname, "connectionlimit") == 0)
  		{
  			if (dconnlimit)
  				ereport(ERROR,
--- 1343,1349 ----
  	{
  		DefElem    *defel = (DefElem *) lfirst(option);
  
! 		if (strcmp(defel->defname, "connection_limit") == 0)
  		{
  			if (dconnlimit)
  				ereport(ERROR,
***************
*** 1374,1380 **** AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
  
  	if (dconnlimit)
  	{
! 		connlimit = intVal(dconnlimit->arg);
  		if (connlimit < -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
--- 1376,1382 ----
  
  	if (dconnlimit)
  	{
! 		connlimit = defGetInt32(dconnlimit);
  		if (connlimit < -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 261,270 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  
  %type <dbehavior>	opt_drop_behavior
  
! %type <list>	createdb_opt_list alterdb_opt_list copy_opt_list
  				transaction_mode_list
  				create_extension_opt_list alter_extension_opt_list
! %type <defelt>	createdb_opt_item alterdb_opt_item copy_opt_item
  				transaction_mode_item
  				create_extension_opt_item alter_extension_opt_item
  
--- 261,270 ----
  
  %type <dbehavior>	opt_drop_behavior
  
! %type <list>	createdb_opt_list createdb_opt_items copy_opt_list
  				transaction_mode_list
  				create_extension_opt_list alter_extension_opt_list
! %type <defelt>	createdb_opt_item copy_opt_item
  				transaction_mode_item
  				create_extension_opt_item alter_extension_opt_item
  
***************
*** 459,464 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
--- 459,465 ----
  %type <list>	var_list
  %type <str>		ColId ColLabel var_name type_function_name param_name
  %type <str>		NonReservedWord NonReservedWord_or_Sconst
+ %type <str>		createdb_opt_name
  %type <node>	var_value zone_value
  
  %type <keyword> unreserved_keyword type_func_name_keyword
***************
*** 561,567 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  
  	KEY
  
! 	LABEL LANGUAGE LARGE_P LAST_P LATERAL_P LC_COLLATE_P LC_CTYPE_P
  	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
  	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P
  
--- 562,568 ----
  
  	KEY
  
! 	LABEL LANGUAGE LARGE_P LAST_P LATERAL_P
  	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
  	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P
  
***************
*** 8317,8394 **** CreatedbStmt:
  		;
  
  createdb_opt_list:
! 			createdb_opt_list createdb_opt_item		{ $$ = lappend($1, $2); }
  			| /* EMPTY */							{ $$ = NIL; }
  		;
  
  createdb_opt_item:
! 			TABLESPACE opt_equal name
! 				{
! 					$$ = makeDefElem("tablespace", (Node *)makeString($3));
! 				}
! 			| TABLESPACE opt_equal DEFAULT
! 				{
! 					$$ = makeDefElem("tablespace", NULL);
! 				}
! 			| LOCATION opt_equal Sconst
! 				{
! 					$$ = makeDefElem("location", (Node *)makeString($3));
! 				}
! 			| LOCATION opt_equal DEFAULT
! 				{
! 					$$ = makeDefElem("location", NULL);
! 				}
! 			| TEMPLATE opt_equal name
! 				{
! 					$$ = makeDefElem("template", (Node *)makeString($3));
! 				}
! 			| TEMPLATE opt_equal DEFAULT
! 				{
! 					$$ = makeDefElem("template", NULL);
! 				}
! 			| ENCODING opt_equal Sconst
! 				{
! 					$$ = makeDefElem("encoding", (Node *)makeString($3));
! 				}
! 			| ENCODING opt_equal Iconst
! 				{
! 					$$ = makeDefElem("encoding", (Node *)makeInteger($3));
! 				}
! 			| ENCODING opt_equal DEFAULT
! 				{
! 					$$ = makeDefElem("encoding", NULL);
! 				}
! 			| LC_COLLATE_P opt_equal Sconst
! 				{
! 					$$ = makeDefElem("lc_collate", (Node *)makeString($3));
! 				}
! 			| LC_COLLATE_P opt_equal DEFAULT
! 				{
! 					$$ = makeDefElem("lc_collate", NULL);
! 				}
! 			| LC_CTYPE_P opt_equal Sconst
  				{
! 					$$ = makeDefElem("lc_ctype", (Node *)makeString($3));
  				}
! 			| LC_CTYPE_P opt_equal DEFAULT
  				{
! 					$$ = makeDefElem("lc_ctype", NULL);
  				}
! 			| CONNECTION LIMIT opt_equal SignedIconst
  				{
! 					$$ = makeDefElem("connectionlimit", (Node *)makeInteger($4));
! 				}
! 			| OWNER opt_equal name
! 				{
! 					$$ = makeDefElem("owner", (Node *)makeString($3));
! 				}
! 			| OWNER opt_equal DEFAULT
! 				{
! 					$$ = makeDefElem("owner", NULL);
  				}
  		;
  
  /*
   *	Though the equals sign doesn't match other WITH options, pg_dump uses
   *	equals for backward compatibility, and it doesn't seem worth removing it.
   */
--- 8318,8369 ----
  		;
  
  createdb_opt_list:
! 			createdb_opt_items						{ $$ = $1; }
  			| /* EMPTY */							{ $$ = NIL; }
  		;
  
+ createdb_opt_items:
+ 			createdb_opt_item						{ $$ = list_make1($1); }
+ 			| createdb_opt_items createdb_opt_item	{ $$ = lappend($1, $2); }
+ 		;
+ 
  createdb_opt_item:
! 			createdb_opt_name opt_equal SignedIconst
  				{
! 					$$ = makeDefElem($1, (Node *)makeInteger($3));
  				}
! 			| createdb_opt_name opt_equal opt_boolean_or_string
  				{
! 					$$ = makeDefElem($1, (Node *)makeString($3));
  				}
! 			| createdb_opt_name opt_equal DEFAULT
  				{
! 					$$ = makeDefElem($1, NULL);
  				}
  		;
  
  /*
+  * Ideally we'd use ColId here, but that causes shift/reduce conflicts against
+  * the ALTER DATABASE SET/RESET syntaxes.  Instead call out specific keywords
+  * we need, and allow IDENT so that database option names don't have to be
+  * parser keywords unless they are already keywords for other reasons.
+  *
+  * XXX this coding technique is fragile since if someone makes a formerly
+  * non-keyword option name into a keyword and forgets to add it here, the
+  * option will silently break.  Best defense is to provide a regression test
+  * exercising every such option, at least at the syntax level.
+  */
+ createdb_opt_name:
+ 			IDENT							{ $$ = $1; }
+ 			| CONNECTION LIMIT				{ $$ = pstrdup("connection_limit"); }
+ 			| ENCODING						{ $$ = pstrdup($1); }
+ 			| LOCATION						{ $$ = pstrdup($1); }
+ 			| OWNER							{ $$ = pstrdup($1); }
+ 			| TABLESPACE					{ $$ = pstrdup($1); }
+ 			| TEMPLATE						{ $$ = pstrdup($1); }
+ 		;
+ 
+ /*
   *	Though the equals sign doesn't match other WITH options, pg_dump uses
   *	equals for backward compatibility, and it doesn't seem worth removing it.
   */
***************
*** 8404,8416 **** opt_equal:	'='										{}
   *****************************************************************************/
  
  AlterDatabaseStmt:
! 			ALTER DATABASE database_name opt_with alterdb_opt_list
  				 {
  					AlterDatabaseStmt *n = makeNode(AlterDatabaseStmt);
  					n->dbname = $3;
  					n->options = $5;
  					$$ = (Node *)n;
  				 }
  			| ALTER DATABASE database_name SET TABLESPACE name
  				 {
  					AlterDatabaseStmt *n = makeNode(AlterDatabaseStmt);
--- 8379,8398 ----
   *****************************************************************************/
  
  AlterDatabaseStmt:
! 			ALTER DATABASE database_name WITH createdb_opt_list
  				 {
  					AlterDatabaseStmt *n = makeNode(AlterDatabaseStmt);
  					n->dbname = $3;
  					n->options = $5;
  					$$ = (Node *)n;
  				 }
+ 			| ALTER DATABASE database_name createdb_opt_list
+ 				 {
+ 					AlterDatabaseStmt *n = makeNode(AlterDatabaseStmt);
+ 					n->dbname = $3;
+ 					n->options = $4;
+ 					$$ = (Node *)n;
+ 				 }
  			| ALTER DATABASE database_name SET TABLESPACE name
  				 {
  					AlterDatabaseStmt *n = makeNode(AlterDatabaseStmt);
***************
*** 8432,8450 **** AlterDatabaseSetStmt:
  		;
  
  
- alterdb_opt_list:
- 			alterdb_opt_list alterdb_opt_item		{ $$ = lappend($1, $2); }
- 			| /* EMPTY */							{ $$ = NIL; }
- 		;
- 
- alterdb_opt_item:
- 			CONNECTION LIMIT opt_equal SignedIconst
- 				{
- 					$$ = makeDefElem("connectionlimit", (Node *)makeInteger($4));
- 				}
- 		;
- 
- 
  /*****************************************************************************
   *
   *		DROP DATABASE [ IF EXISTS ]
--- 8414,8419 ----
***************
*** 12912,12919 **** unreserved_keyword:
  			| LANGUAGE
  			| LARGE_P
  			| LAST_P
- 			| LC_COLLATE_P
- 			| LC_CTYPE_P
  			| LEAKPROOF
  			| LEVEL
  			| LISTEN
--- 12881,12886 ----
*** a/src/bin/pg_dump/pg_dumpall.c
--- b/src/bin/pg_dump/pg_dumpall.c
***************
*** 1375,1381 **** dumpCreateDB(PGconn *conn)
  								  fmtId(dbtablespace));
  
  			if (strcmp(dbconnlimit, "-1") != 0)
! 				appendPQExpBuffer(buf, " CONNECTION LIMIT = %s",
  								  dbconnlimit);
  
  			appendPQExpBufferStr(buf, ";\n");
--- 1375,1381 ----
  								  fmtId(dbtablespace));
  
  			if (strcmp(dbconnlimit, "-1") != 0)
! 				appendPQExpBuffer(buf, " CONNECTION_LIMIT = %s",
  								  dbconnlimit);
  
  			appendPQExpBufferStr(buf, ";\n");
*** a/src/bin/psql/tab-complete.c
--- b/src/bin/psql/tab-complete.c
***************
*** 1004,1010 **** psql_completion(const char *text, int start, int end)
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_ALTERDATABASE[] =
! 		{"RESET", "SET", "OWNER TO", "RENAME TO", "CONNECTION LIMIT", NULL};
  
  		COMPLETE_WITH_LIST(list_ALTERDATABASE);
  	}
--- 1004,1010 ----
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_ALTERDATABASE[] =
! 		{"RESET", "SET", "OWNER TO", "RENAME TO", "CONNECTION_LIMIT", NULL};
  
  		COMPLETE_WITH_LIST(list_ALTERDATABASE);
  	}
***************
*** 2045,2051 **** psql_completion(const char *text, int start, int end)
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_DATABASE[] =
! 		{"OWNER", "TEMPLATE", "ENCODING", "TABLESPACE", "CONNECTION LIMIT",
  		NULL};
  
  		COMPLETE_WITH_LIST(list_DATABASE);
--- 2045,2051 ----
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_DATABASE[] =
! 		{"OWNER", "TEMPLATE", "ENCODING", "TABLESPACE", "CONNECTION_LIMIT",
  		NULL};
  
  		COMPLETE_WITH_LIST(list_DATABASE);
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 215,222 **** PG_KEYWORD("language", LANGUAGE, UNRESERVED_KEYWORD)
  PG_KEYWORD("large", LARGE_P, UNRESERVED_KEYWORD)
  PG_KEYWORD("last", LAST_P, UNRESERVED_KEYWORD)
  PG_KEYWORD("lateral", LATERAL_P, RESERVED_KEYWORD)
- PG_KEYWORD("lc_collate", LC_COLLATE_P, UNRESERVED_KEYWORD)
- PG_KEYWORD("lc_ctype", LC_CTYPE_P, UNRESERVED_KEYWORD)
  PG_KEYWORD("leading", LEADING, RESERVED_KEYWORD)
  PG_KEYWORD("leakproof", LEAKPROOF, UNRESERVED_KEYWORD)
  PG_KEYWORD("least", LEAST, COL_NAME_KEYWORD)
--- 215,220 ----

*** a/contrib/pg_upgrade/pg_upgrade.c
--- b/contrib/pg_upgrade/pg_upgrade.c
***************
*** 519,527 **** set_frozenxids(void)
  		 */
  		if (strcmp(datallowconn, "f") == 0)
  			PQclear(executeQueryOrDie(conn_template1,
! 									  "UPDATE pg_catalog.pg_database "
! 									  "SET	datallowconn = true "
! 									  "WHERE datname = '%s'", datname));
  
  		conn = connectToServer(&new_cluster, datname);
  
--- 519,526 ----
  		 */
  		if (strcmp(datallowconn, "f") == 0)
  			PQclear(executeQueryOrDie(conn_template1,
! 									  "ALTER DATABASE %s ALLOW_CONNECTIONS = true",
! 									  datname));
  
  		conn = connectToServer(&new_cluster, datname);
  
***************
*** 537,545 **** set_frozenxids(void)
  		/* Reset datallowconn flag */
  		if (strcmp(datallowconn, "f") == 0)
  			PQclear(executeQueryOrDie(conn_template1,
! 									  "UPDATE pg_catalog.pg_database "
! 									  "SET	datallowconn = false "
! 									  "WHERE datname = '%s'", datname));
  	}
  
  	PQclear(dbres);
--- 536,543 ----
  		/* Reset datallowconn flag */
  		if (strcmp(datallowconn, "f") == 0)
  			PQclear(executeQueryOrDie(conn_template1,
! 									  "ALTER DATABASE %s ALLOW_CONNECTIONS = false",
! 									  datname));
  	}
  
  	PQclear(dbres);
*** a/doc/src/sgml/ref/alter_database.sgml
--- b/doc/src/sgml/ref/alter_database.sgml
***************
*** 25,30 **** ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> [ [ WITH ] <rep
--- 25,32 ----
  
  <phrase>where <replaceable class="PARAMETER">option</replaceable> can be:</phrase>
  
+     IS_TEMPLATE <replaceable class="PARAMETER">istemplate</replaceable>
+     ALLOW_CONNECTIONS <replaceable class="PARAMETER">allowconn</replaceable>
      CONNECTION_LIMIT <replaceable class="PARAMETER">connection_limit</replaceable>
  
  ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable>new_name</replaceable>
***************
*** 107,112 **** ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RESET ALL
--- 109,134 ----
       </varlistentry>
  
       <varlistentry>
+        <term><replaceable class="parameter">istemplate</replaceable></term>
+        <listitem>
+         <para>
+          If true, then this database can be cloned by any user with CREATEDB
+          privileges; if false, then only superusers or the owner of the
+          database can clone it.
+         </para>
+        </listitem>
+       </varlistentry>
+  
+       <varlistentry>
+        <term><replaceable class="parameter">allowconn</replaceable></term>
+        <listitem>
+         <para>
+          If false then no one can connect to this database.
+         </para>
+        </listitem>
+       </varlistentry>
+  
+       <varlistentry>
        <term><replaceable class="parameter">connection_limit</replaceable></term>
        <listitem>
         <para>
*** a/doc/src/sgml/ref/create_database.sgml
--- b/doc/src/sgml/ref/create_database.sgml
***************
*** 28,33 **** CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
--- 28,35 ----
             [ LC_COLLATE [=] <replaceable class="parameter">lc_collate</replaceable> ]
             [ LC_CTYPE [=] <replaceable class="parameter">lc_ctype</replaceable> ]
             [ TABLESPACE [=] <replaceable class="parameter">tablespace_name</replaceable> ]
+            [ IS_TEMPLATE [=] <replaceable class="parameter">istemplate</replaceable>]
+            [ ALLOW_CONNECTIONS [=] <replaceable class="parameter">allowconn</replaceable>]
             [ CONNECTION_LIMIT [=] <replaceable class="parameter">connection_limit</replaceable> ] ]
  </synopsis>
   </refsynopsisdiv>
***************
*** 148,153 **** CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
--- 150,175 ----
       </varlistentry>
  
       <varlistentry>
+        <term><replaceable class="parameter">istemplate</replaceable></term>
+        <listitem>
+         <para>
+          If true, then this database can be cloned by any user with CREATEDB
+          privileges; if false, then only superusers or the owner of the
+          database can clone it.
+         </para>
+        </listitem>
+       </varlistentry>
+  
+       <varlistentry>
+        <term><replaceable class="parameter">allowconn</replaceable></term>
+        <listitem>
+         <para>
+          If false then no one can connect to this database.
+         </para>
+        </listitem>
+       </varlistentry>
+  
+       <varlistentry>
        <term><replaceable class="parameter">connection_limit</replaceable></term>
        <listitem>
         <para>
*** a/src/backend/commands/dbcommands.c
--- b/src/backend/commands/dbcommands.c
***************
*** 123,128 **** createdb(const CreatedbStmt *stmt)
--- 123,130 ----
  	DefElem    *dencoding = NULL;
  	DefElem    *dcollate = NULL;
  	DefElem    *dctype = NULL;
+ 	DefElem	   *distemplate = NULL;
+ 	DefElem	   *dallowconnections = NULL;
  	DefElem    *dconnlimit = NULL;
  	char	   *dbname = stmt->dbname;
  	char	   *dbowner = NULL;
***************
*** 131,136 **** createdb(const CreatedbStmt *stmt)
--- 133,140 ----
  	char	   *dbctype = NULL;
  	char	   *canonname;
  	int			encoding = -1;
+ 	bool		dbistemplate = false;
+ 	bool		dballowconnections = true;
  	int			dbconnlimit = -1;
  	int			notherbackends;
  	int			npreparedxacts;
***************
*** 189,194 **** createdb(const CreatedbStmt *stmt)
--- 193,214 ----
  						 errmsg("conflicting or redundant options")));
  			dctype = defel;
  		}
+ 		else if (strcmp(defel->defname, "is_template") == 0)
+ 		{
+ 			if (distemplate)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_SYNTAX_ERROR),
+ 						 errmsg("conflicting or redundant options")));
+ 			distemplate = defel;
+ 		}
+ 		else if (strcmp(defel->defname, "allow_connections") == 0)
+ 		{
+ 			if (dallowconnections)
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_SYNTAX_ERROR),
+ 						 errmsg("conflicting or redundant options")));
+ 			dallowconnections = defel;
+ 		}
  		else if (strcmp(defel->defname, "connection_limit") == 0)
  		{
  			if (dconnlimit)
***************
*** 248,253 **** createdb(const CreatedbStmt *stmt)
--- 268,277 ----
  	if (dctype)
  		dbctype = defGetString(dctype);
  
+ 	if (distemplate)
+ 		dbistemplate = defGetBoolean(distemplate);
+ 	if (dallowconnections)
+ 		dballowconnections = defGetBoolean(dallowconnections);
  	if (dconnlimit)
  	{
  		dbconnlimit = defGetInt32(dconnlimit);
***************
*** 490,497 **** createdb(const CreatedbStmt *stmt)
  		DirectFunctionCall1(namein, CStringGetDatum(dbcollate));
  	new_record[Anum_pg_database_datctype - 1] =
  		DirectFunctionCall1(namein, CStringGetDatum(dbctype));
! 	new_record[Anum_pg_database_datistemplate - 1] = BoolGetDatum(false);
! 	new_record[Anum_pg_database_datallowconn - 1] = BoolGetDatum(true);
  	new_record[Anum_pg_database_datconnlimit - 1] = Int32GetDatum(dbconnlimit);
  	new_record[Anum_pg_database_datlastsysoid - 1] = ObjectIdGetDatum(src_lastsysoid);
  	new_record[Anum_pg_database_datfrozenxid - 1] = TransactionIdGetDatum(src_frozenxid);
--- 514,521 ----
  		DirectFunctionCall1(namein, CStringGetDatum(dbcollate));
  	new_record[Anum_pg_database_datctype - 1] =
  		DirectFunctionCall1(namein, CStringGetDatum(dbctype));
! 	new_record[Anum_pg_database_datistemplate - 1] = BoolGetDatum(dbistemplate);
! 	new_record[Anum_pg_database_datallowconn - 1] = BoolGetDatum(dballowconnections);
  	new_record[Anum_pg_database_datconnlimit - 1] = Int32GetDatum(dbconnlimit);
  	new_record[Anum_pg_database_datlastsysoid - 1] = ObjectIdGetDatum(src_lastsysoid);
  	new_record[Anum_pg_database_datfrozenxid - 1] = TransactionIdGetDatum(src_frozenxid);
***************
*** 1331,1337 **** AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
  	ScanKeyData scankey;
  	SysScanDesc scan;
  	ListCell   *option;
! 	int			connlimit = -1;
  	DefElem    *dconnlimit = NULL;
  	DefElem    *dtablespace = NULL;
  	Datum		new_record[Natts_pg_database];
--- 1355,1365 ----
  	ScanKeyData scankey;
  	SysScanDesc scan;
  	ListCell   *option;
! 	bool		dbistemplate = false;
! 	bool		dballowconnections = true;
! 	int			dbconnlimit = -1;
! 	DefElem	   *distemplate = NULL;
! 	DefElem	   *dallowconnections = NULL;
  	DefElem    *dconnlimit = NULL;
  	DefElem    *dtablespace = NULL;
  	Datum		new_record[Natts_pg_database];
***************
*** 1343,1349 **** AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
  	{
  		DefElem    *defel = (DefElem *) lfirst(option);
  
! 		if (strcmp(defel->defname, "connection_limit") == 0)
  		{
  			if (dconnlimit)
  				ereport(ERROR,
--- 1371,1393 ----
  	{
  		DefElem    *defel = (DefElem *) lfirst(option);
  
! 		if (strcmp(defel->defname, "is_template") == 0)
! 		{
! 			if (distemplate)
! 				ereport(ERROR,
! 						(errcode(ERRCODE_SYNTAX_ERROR),
! 						 errmsg("conflicting or redundant options")));
! 			distemplate = defel;
! 		}
! 		else if (strcmp(defel->defname, "allow_connections") == 0)
! 		{
! 			if (dallowconnections)
! 				ereport(ERROR,
! 						(errcode(ERRCODE_SYNTAX_ERROR),
! 						 errmsg("conflicting or redundant options")));
! 			dallowconnections = defel;
! 		}
! 		else if (strcmp(defel->defname, "connection_limit") == 0)
  		{
  			if (dconnlimit)
  				ereport(ERROR,
***************
*** 1367,1386 **** AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
  	if (dtablespace)
  	{
  		/* currently, can't be specified along with any other options */
! 		Assert(!dconnlimit);
  		/* this case isn't allowed within a transaction block */
  		PreventTransactionChain(isTopLevel, "ALTER DATABASE SET TABLESPACE");
  		movedb(stmt->dbname, strVal(dtablespace->arg));
  		return InvalidOid;
  	}
  
  	if (dconnlimit)
  	{
! 		connlimit = defGetInt32(dconnlimit);
! 		if (connlimit < -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 					 errmsg("invalid connection limit: %d", connlimit)));
  	}
  
  	/*
--- 1411,1434 ----
  	if (dtablespace)
  	{
  		/* currently, can't be specified along with any other options */
! 		Assert(!distemplate && !dallowconnections && !dconnlimit);
  		/* this case isn't allowed within a transaction block */
  		PreventTransactionChain(isTopLevel, "ALTER DATABASE SET TABLESPACE");
  		movedb(stmt->dbname, strVal(dtablespace->arg));
  		return InvalidOid;
  	}
  
+ 	if (distemplate)
+ 		dbistemplate = defGetBoolean(distemplate);
+ 	if (dallowconnections)
+ 		dballowconnections = defGetBoolean(dallowconnections);
  	if (dconnlimit)
  	{
! 		dbconnlimit = defGetInt32(dconnlimit);
! 		if (dbconnlimit < -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 					 errmsg("invalid connection limit: %d", dbconnlimit)));
  	}
  
  	/*
***************
*** 1408,1422 **** AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
  					   stmt->dbname);
  
  	/*
  	 * Build an updated tuple, perusing the information just obtained
  	 */
  	MemSet(new_record, 0, sizeof(new_record));
  	MemSet(new_record_nulls, false, sizeof(new_record_nulls));
  	MemSet(new_record_repl, false, sizeof(new_record_repl));
  
  	if (dconnlimit)
  	{
! 		new_record[Anum_pg_database_datconnlimit - 1] = Int32GetDatum(connlimit);
  		new_record_repl[Anum_pg_database_datconnlimit - 1] = true;
  	}
  
--- 1456,1491 ----
  					   stmt->dbname);
  
  	/*
+ 	 * In order to avoid getting locked out and having to go through standalone
+ 	 * mode, we refuse to disallow connections on the database we're currently
+ 	 * connected to.  Lockout can still happen with concurrent sessions but the
+ 	 * likeliness of that is not high enough to worry about.
+ 	 */
+ 	if (!dballowconnections && dboid == MyDatabaseId)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 				 errmsg("cannot disallow connections for current database")));
+ 
+ 	/*
  	 * Build an updated tuple, perusing the information just obtained
  	 */
  	MemSet(new_record, 0, sizeof(new_record));
  	MemSet(new_record_nulls, false, sizeof(new_record_nulls));
  	MemSet(new_record_repl, false, sizeof(new_record_repl));
  
+ 	if (distemplate)
+ 	{
+ 		new_record[Anum_pg_database_datistemplate - 1] = BoolGetDatum(dbistemplate);
+ 		new_record_repl[Anum_pg_database_datistemplate - 1] = true;
+ 	}
+ 	if (dallowconnections)
+ 	{
+ 		new_record[Anum_pg_database_datallowconn - 1] = BoolGetDatum(dballowconnections);
+ 		new_record_repl[Anum_pg_database_datallowconn - 1] = true;
+ 	}
  	if (dconnlimit)
  	{
! 		new_record[Anum_pg_database_datconnlimit - 1] = Int32GetDatum(dbconnlimit);
  		new_record_repl[Anum_pg_database_datconnlimit - 1] = true;
  	}
  
*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 2288,2298 **** make_template0(void)
  	PG_CMD_DECL;
  	const char **line;
  	static const char *template0_setup[] = {
! 		"CREATE DATABASE template0;\n",
! 		"UPDATE pg_database SET "
! 		"	datistemplate = 't', "
! 		"	datallowconn = 'f' "
! 		"    WHERE datname = 'template0';\n",
  
  		/*
  		 * We use the OID of template0 to determine lastsysoid
--- 2288,2294 ----
  	PG_CMD_DECL;
  	const char **line;
  	static const char *template0_setup[] = {
! 		"CREATE DATABASE template0 IS_TEMPLATE = true ALLOW_CONNECTIONS = false;\n",
  
  		/*
  		 * We use the OID of template0 to determine lastsysoid
*** a/src/bin/pg_dump/pg_dumpall.c
--- b/src/bin/pg_dump/pg_dumpall.c
***************
*** 1374,1392 **** dumpCreateDB(PGconn *conn)
  				appendPQExpBuffer(buf, " TABLESPACE = %s",
  								  fmtId(dbtablespace));
  
  			if (strcmp(dbconnlimit, "-1") != 0)
  				appendPQExpBuffer(buf, " CONNECTION_LIMIT = %s",
  								  dbconnlimit);
  
  			appendPQExpBufferStr(buf, ";\n");
  
- 			if (strcmp(dbistemplate, "t") == 0)
- 			{
- 				appendPQExpBufferStr(buf, "UPDATE pg_catalog.pg_database SET datistemplate = 't' WHERE datname = ");
- 				appendStringLiteralConn(buf, dbname, conn);
- 				appendPQExpBufferStr(buf, ";\n");
- 			}
- 
  			if (binary_upgrade)
  			{
  				appendPQExpBufferStr(buf, "-- For binary upgrade, set datfrozenxid.\n");
--- 1374,1388 ----
  				appendPQExpBuffer(buf, " TABLESPACE = %s",
  								  fmtId(dbtablespace));
  
+ 			if (strcmp(dbistemplate, "t") == 0)
+ 				appendPQExpBuffer(buf, " IS_TEMPLATE = true");
+ 
  			if (strcmp(dbconnlimit, "-1") != 0)
  				appendPQExpBuffer(buf, " CONNECTION_LIMIT = %s",
  								  dbconnlimit);
  
  			appendPQExpBufferStr(buf, ";\n");
  
  			if (binary_upgrade)
  			{
  				appendPQExpBufferStr(buf, "-- For binary upgrade, set datfrozenxid.\n");
*** a/src/bin/psql/tab-complete.c
--- b/src/bin/psql/tab-complete.c
***************
*** 1004,1010 **** psql_completion(const char *text, int start, int end)
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_ALTERDATABASE[] =
! 		{"RESET", "SET", "OWNER TO", "RENAME TO", "CONNECTION_LIMIT", NULL};
  
  		COMPLETE_WITH_LIST(list_ALTERDATABASE);
  	}
--- 1004,1011 ----
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_ALTERDATABASE[] =
! 		{"RESET", "SET", "OWNER TO", "RENAME TO", "IS_TEMPLATE",
! 		"ALLOW_CONNECTIONS", "CONNECTION_LIMIT", NULL};
  
  		COMPLETE_WITH_LIST(list_ALTERDATABASE);
  	}
***************
*** 2045,2052 **** psql_completion(const char *text, int start, int end)
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_DATABASE[] =
! 		{"OWNER", "TEMPLATE", "ENCODING", "TABLESPACE", "CONNECTION_LIMIT",
! 		NULL};
  
  		COMPLETE_WITH_LIST(list_DATABASE);
  	}
--- 2046,2053 ----
  			 pg_strcasecmp(prev2_wd, "DATABASE") == 0)
  	{
  		static const char *const list_DATABASE[] =
! 		{"OWNER", "TEMPLATE", "ENCODING", "TABLESPACE", "IS_TEMPLATE",
! 		"ALLOW_CONNECTIONS", "CONNECTION_LIMIT", NULL};
  
  		COMPLETE_WITH_LIST(list_DATABASE);
  	}