pl/python custom datatype parsers

diff --git a/contrib/hstore/Makefile b/contrib/hstore/Makefile
index 1d533fd..4e6ba7b 100644
*** a/contrib/hstore/Makefile
--- b/contrib/hstore/Makefile
***************
*** 1,8 ****
  # contrib/hstore/Makefile
  
  MODULE_big = hstore
  OBJS = hstore_io.o hstore_op.o hstore_gist.o hstore_gin.o hstore_compat.o \
! 	crc32.o
  
  DATA_built = hstore.sql
  DATA = uninstall_hstore.sql
--- 1,17 ----
  # contrib/hstore/Makefile
  
  MODULE_big = hstore
+ 
  OBJS = hstore_io.o hstore_op.o hstore_gist.o hstore_gin.o hstore_compat.o \
! 	hstore_plpython.o crc32.o
! 
! ifeq ($(with_python),yes)
! 
! PG_CPPFLAGS := -I$(srcdir) -I$(top_builddir)/src/pl/plpython \
! 			$(python_includespec) -DHSTORE_PLPYTHON_SUPPORT
! SHLIB_LINK = $(python_libspec) $(python_additional_libs) \
! 		$(filter -lintl,$(LIBS)) $(CPPFLAGS)
! endif
  
  DATA_built = hstore.sql
  DATA = uninstall_hstore.sql
diff --git a/contrib/hstore/hstore.h b/contrib/hstore/hstore.h
index 8906397..6edfc70 100644
*** a/contrib/hstore/hstore.h
--- b/contrib/hstore/hstore.h
*************** extern Pairs *hstoreArrayToPairs(ArrayTy
*** 174,179 ****
--- 174,182 ----
  #define HStoreExistsAllStrategyNumber	11
  #define HStoreOldContainsStrategyNumber 13		/* backwards compatibility */
  
+ /* PL/Python support */
+ extern void hstore_plpython_init(void);
+ 
  /*
   * defining HSTORE_POLLUTE_NAMESPACE=0 will prevent use of old function names;
   * for now, we default to on for the benefit of people restoring old dumps
diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 0d6f0b6..92c8db9 100644
*** a/contrib/hstore/hstore_io.c
--- b/contrib/hstore/hstore_io.c
*************** PG_MODULE_MAGIC;
*** 20,25 ****
--- 20,26 ----
  /* old names for C functions */
  HSTORE_POLLUTE(hstore_from_text, tconvert);
  
+ void _PG_init(void);
  
  typedef struct
  {
*************** hstore_send(PG_FUNCTION_ARGS)
*** 1211,1213 ****
--- 1212,1220 ----
  
  	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
  }
+ 
+ void
+ _PG_init(void)
+ {
+ 	hstore_plpython_init();
+ }
diff --git a/contrib/hstore/hstore_plpython.c b/contrib/hstore/hstore_plpython.c
index ...4ba111a .
*** a/contrib/hstore/hstore_plpython.c
--- b/contrib/hstore/hstore_plpython.c
***************
*** 0 ****
--- 1,251 ----
+ /*
+  * contrib/src/hstore_plpython.c
+  *
+  * bidirectional transformation between hstores and Python dictionary objects
+  */
+ 
+ /* Only build if PL/Python support is needed */
+ #if defined(HSTORE_PLPYTHON_SUPPORT)
+ 
+ #if defined(_MSC_VER) && defined(_DEBUG)
+ /* Python uses #pragma to bring in a non-default libpython on VC++ if
+  * _DEBUG is defined */
+ #undef _DEBUG
+ /* Also hide away errcode, since we load Python.h before postgres.h */
+ #define errcode __msvc_errcode
+ #include <Python.h>
+ #undef errcode
+ #define _DEBUG
+ #elif defined (_MSC_VER)
+ #define errcode __msvc_errcode
+ #include <Python.h>
+ #undef errcode
+ #else
+ #include <Python.h>
+ #endif
+ 
+ #include "postgres.h"
+ #include "utils/guc.h"
+ #include "utils/builtins.h"
+ #include "utils/syscache.h"
+ #include "catalog/namespace.h"
+ 
+ #include "plpython.h"
+ #include "hstore.h"
+ 
+ static Oid get_hstore_oid(const char *name);
+ static void set_hstore_parsers(Oid);
+ 
+ static PyObject *hstore_to_dict(void *, Datum);
+ static Datum dict_to_hstore(void *, int32, PyObject *);
+ 
+ /* GUC variables */
+ 
+ static char *hstore_name;
+ 
+ /* Previous hstore OID */
+ 
+ static Oid previous;
+ 
+ PLyParsers parsers = {
+ 	.in = hstore_to_dict,
+ 	.out = dict_to_hstore
+ };
+ 
+ static PyObject *
+ hstore_to_dict(void *ignored, Datum d)
+ {
+ 	HStore		*hstore = DatumGetHStoreP(d);
+     char        *base;
+     HEntry      *entries;
+     int          count;
+     int          i;
+     PyObject    *ret;
+ 
+ 	base = STRPTR(hstore);
+     entries = ARRPTR(hstore);
+ 
+     ret = PyDict_New();
+ 
+     count = HS_COUNT(hstore);
+ 
+     for (i = 0; i < count; i++)
+ 	{
+             PyObject *key, *val;
+ 
+             key = PyString_FromStringAndSize(HS_KEY(entries, base, i),
+                                              HS_KEYLEN(entries, i));
+             if (HS_VALISNULL(entries, i)) {
+                 Py_INCREF(Py_None);
+                 val = Py_None;
+             }
+             else {
+                 val = PyString_FromStringAndSize(HS_VAL(entries, base, i),
+                                                  HS_VALLEN(entries, i));
+             }
+ 
+             PyDict_SetItem(ret, key, val);
+         }
+ 
+     return ret;
+ }
+ 
+ static Datum
+ dict_to_hstore(void *ignored, int32 typmod, PyObject *dict)
+ {
+     HStore      *hstore;
+     int          pcount;
+ 	Pairs		*pairs;
+ 	PyObject	*key;
+ 	PyObject	*value;
+ 	Py_ssize_t	 pos;
+ 	char		*keys;
+ 	char		*vals;
+ 	int			 keylen;
+ 	int			 vallen;
+ 	int			 buflen;
+ 	int			 i;
+ 
+ 	if (!PyDict_Check(dict))
+ 		ereport(ERROR,
+ 				(errmsg("hstores can only be constructed "
+ 						"from Python dictionaries")));
+ 
+ 	pcount = PyDict_Size(dict);
+ 	pairs = palloc(pcount * sizeof(Pairs));
+ 	pos = i = 0;
+ 	/* loop over the dictionary, creating a Pair for each key/value pair */
+ 	while (PyDict_Next(dict, &pos, &key, &value)) {
+ 		if (!PyString_Check(key))
+ 			elog(ERROR, "hstore keys have to be strings");
+ 
+ 		PyString_AsStringAndSize(key, &keys, &keylen);
+ 
+ 		if (strlen(keys) != keylen)
+ 			elog(ERROR, "hstore keys cannot contain NUL bytes");
+ 
+ 		pairs[i].key = pstrdup(keys);
+ 		pairs[i].keylen = hstoreCheckKeyLen(keylen);
+ 		pairs[i].needfree = true;
+ 
+ 		if (value == Py_None) {
+ 			pairs[i].val = NULL;
+ 			pairs[i].vallen = 0;
+ 			pairs[i].isnull = true;
+ 		}
+ 		else {
+ 			if (!PyString_Check(value))
+ 				elog(ERROR, "hstore values have to be strings");
+ 
+ 			PyString_AsStringAndSize(value, &vals, &vallen);
+ 
+ 			if (strlen(vals) != vallen)
+ 				elog(ERROR, "hstore values cannot contain NUL bytes");
+ 
+ 			pairs[i].val = pstrdup(vals);
+ 			pairs[i].vallen = hstoreCheckValLen(vallen);
+ 			pairs[i].isnull = false;
+ 		}
+ 
+ 		i++;
+ 	}
+ 	pcount = hstoreUniquePairs(pairs, pcount, &buflen);
+ 	hstore = hstorePairs(pairs, pcount, buflen);
+ 
+ 	return PointerGetDatum(hstore);
+ }
+ 
+ static const char *
+ recheck_hstore_oid(const char *newvalue, bool doit, GucSource source)
+ {
+ 	Oid	hstore_oid;
+ 
+ 	if (newvalue == NULL)
+ 		return NULL;
+ 
+ 	hstore_oid = get_hstore_oid(newvalue);
+ 
+ 	if (*newvalue && !OidIsValid(hstore_oid))
+ 		return NULL;
+ 
+ 	if (doit)
+ 		set_hstore_parsers(hstore_oid);
+ 
+ 	return newvalue;
+ }
+ 
+ void
+ hstore_plpython_init(void)
+ {
+ 	DefineCustomStringVariable("plpython.hstore",
+ 	  "The fully qualified name of the hstore type.",
+ 							   NULL,
+ 							   &hstore_name,
+ 							   NULL,
+ 							   PGC_SUSET,
+ 							   0,
+ 							   recheck_hstore_oid,
+ 							   NULL);
+ 
+ 	EmitWarningsOnPlaceholders("plpython");
+ 
+ 	previous = InvalidOid;
+ 
+ 	if (hstore_name && *hstore_name)
+ 		recheck_hstore_oid(hstore_name, true, PGC_S_FILE);
+ }
+ 
+ static Oid
+ get_hstore_oid(const char *name)
+ {
+ 	text		*text_name;
+ 	List		*hstore_name;
+ 	char		*type_name;
+ 	Oid			 type_namespace;
+ 	Oid			 typoid;
+ 
+ 	Assert(name != NULL);
+ 
+ 	if (!(*name))
+ 		return InvalidOid;
+ 
+ 	text_name = cstring_to_text(name);
+ 	hstore_name = textToQualifiedNameList(text_name);
+ 	pfree(text_name);
+ 
+ 	type_namespace = QualifiedNameGetCreationNamespace(hstore_name, &type_name);
+ 
+ 	typoid = GetSysCacheOid2(TYPENAMENSP,
+ 							 CStringGetDatum(type_name),
+ 							 ObjectIdGetDatum(type_namespace));
+ 
+ 	return typoid;
+ }
+ 
+ static void
+ set_hstore_parsers(Oid hstore_oid)
+ {
+ 	char		 name[NAMEDATALEN];
+ 
+ 	if (OidIsValid(previous))
+ 	{
+ 		snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, previous);
+ 		*find_rendezvous_variable(name) = NULL;
+ 	}
+ 
+ 	if (OidIsValid(hstore_oid))
+ 	{
+ 		snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, hstore_oid);
+ 		*find_rendezvous_variable(name) = &parsers;
+ 		previous = hstore_oid;
+ 	}
+ }
+ 
+ #else	/* !defined(HSTORE_PLPYTHON_SUPPORT) */
+ 
+ extern void hstore_plpython_init(void);
+ 
+ void
+ hstore_plpython_init(void) {};
+ 
+ #endif	/* defined(HSTORE_PLPYTHON_SUPPORT) */
diff --git a/src/pl/plpython/plpython.c b/src/pl/plpython/plpython.c
index aafe556..8841af1 100644
*** a/src/pl/plpython/plpython.c
--- b/src/pl/plpython/plpython.c
*************** typedef int Py_ssize_t;
*** 90,95 ****
--- 90,97 ----
  #include <fcntl.h>
  
  /* postgreSQL stuff */
+ #include "plpython.h"
+ 
  #include "catalog/pg_proc.h"
  #include "catalog/pg_type.h"
  #include "commands/trigger.h"
*************** static PyObject *PLyList_FromArray(PLyDa
*** 354,359 ****
--- 356,364 ----
  
  static PyObject *PLyDict_FromTuple(PLyTypeInfo *, HeapTuple, TupleDesc);
  
+ static PLyParserIn PLy_get_custom_input_function(Oid oid);
+ static PLyParserOut PLy_get_custom_output_function(Oid oid);
+ 
  static Datum PLyObject_ToBool(PLyObToDatum *, int32, PyObject *);
  static Datum PLyObject_ToBytea(PLyObToDatum *, int32, PyObject *);
  static Datum PLyObject_ToDatum(PLyObToDatum *, int32, PyObject *);
*************** PLy_output_datum_func2(PLyObToDatum *arg
*** 1779,1784 ****
--- 1784,1790 ----
  {
  	Form_pg_type typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
  	Oid			element_type;
+ 	Oid			argument_type;
  
  	perm_fmgr_info(typeStruct->typinput, &arg->typfunc);
  	arg->typoid = HeapTupleGetOid(typeTup);
*************** PLy_output_datum_func2(PLyObToDatum *arg
*** 1786,1797 ****
  	arg->typbyval = typeStruct->typbyval;
  
  	element_type = get_element_type(arg->typoid);
  
  	/*
  	 * Select a conversion function to convert Python objects to PostgreSQL
  	 * datums.	Most data types can go through the generic function.
  	 */
! 	switch (getBaseType(element_type ? element_type : arg->typoid))
  	{
  		case BOOLOID:
  			arg->func = PLyObject_ToBool;
--- 1792,1804 ----
  	arg->typbyval = typeStruct->typbyval;
  
  	element_type = get_element_type(arg->typoid);
+ 	argument_type = getBaseType(element_type ? element_type : arg->typoid);
  
  	/*
  	 * Select a conversion function to convert Python objects to PostgreSQL
  	 * datums.	Most data types can go through the generic function.
  	 */
! 	switch (argument_type)
  	{
  		case BOOLOID:
  			arg->func = PLyObject_ToBool;
*************** PLy_output_datum_func2(PLyObToDatum *arg
*** 1800,1806 ****
  			arg->func = PLyObject_ToBytea;
  			break;
  		default:
! 			arg->func = PLyObject_ToDatum;
  			break;
  	}
  
--- 1807,1819 ----
  			arg->func = PLyObject_ToBytea;
  			break;
  		default:
! 			/* Last ditch effort of finding a rendezvous variable pointing to
! 			 * a parser function, useful for extension modules plugging in
! 			 * their own parsers
! 			 */
! 			arg->func = (PLyObToDatumFunc) PLy_get_custom_output_function(argument_type);
! 			if (arg->func == NULL)
! 				arg->func = PLyObject_ToDatum;
  			break;
  	}
  
*************** PLy_input_datum_func2(PLyDatumToOb *arg,
*** 1842,1847 ****
--- 1855,1861 ----
  {
  	Form_pg_type typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
  	Oid			element_type = get_element_type(typeOid);
+ 	Oid			argument_type;
  
  	/* Get the type's conversion information */
  	perm_fmgr_info(typeStruct->typoutput, &arg->typfunc);
*************** PLy_input_datum_func2(PLyDatumToOb *arg,
*** 1851,1858 ****
  	arg->typlen = typeStruct->typlen;
  	arg->typalign = typeStruct->typalign;
  
  	/* Determine which kind of Python object we will convert to */
! 	switch (getBaseType(element_type ? element_type : typeOid))
  	{
  		case BOOLOID:
  			arg->func = PLyBool_FromBool;
--- 1865,1874 ----
  	arg->typlen = typeStruct->typlen;
  	arg->typalign = typeStruct->typalign;
  
+ 	argument_type = getBaseType(element_type ? element_type : typeOid);
+ 
  	/* Determine which kind of Python object we will convert to */
! 	switch (argument_type)
  	{
  		case BOOLOID:
  			arg->func = PLyBool_FromBool;
*************** PLy_input_datum_func2(PLyDatumToOb *arg,
*** 1879,1885 ****
  			arg->func = PLyBytes_FromBytea;
  			break;
  		default:
! 			arg->func = PLyString_FromDatum;
  			break;
  	}
  
--- 1895,1907 ----
  			arg->func = PLyBytes_FromBytea;
  			break;
  		default:
! 			/* Last ditch effort of finding a rendezvous variable pointing to
! 			 * a parser function, useful for extension modules plugging in
! 			 * their own parsers
! 			 */
! 			arg->func = (PLyDatumToObFunc) PLy_get_custom_input_function(argument_type);
! 			if (arg->func == NULL)
! 				arg->func = PLyString_FromDatum;
  			break;
  	}
  
*************** PLy_typeinfo_dealloc(PLyTypeInfo *arg)
*** 1920,1925 ****
--- 1942,1981 ----
  	}
  }
  
+ /*
+  * Getting the parser functions from a rendezvous variable set by another
+  * extension.
+  */
+ static PLyParserIn
+ PLy_get_custom_input_function(Oid oid)
+ {
+ 	PLyParsers	*parsers;
+ 	char		 name[NAMEDATALEN];
+ 
+ 	snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, oid);
+ 	parsers = *find_rendezvous_variable(name);
+ 
+ 	if (parsers == NULL)
+ 		return NULL;
+ 
+ 	return parsers->in;
+ }
+ 
+ static PLyParserOut
+ PLy_get_custom_output_function(Oid oid)
+ {
+ 	PLyParsers	*parsers;
+ 	char		 name[NAMEDATALEN];
+ 
+ 	snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, oid);
+ 	parsers = *find_rendezvous_variable(name);
+ 
+ 	if (parsers == NULL)
+ 		return NULL;
+ 
+ 	return parsers->out;
+ }
+ 
  static PyObject *
  PLyBool_FromBool(PLyDatumToOb *arg, Datum d)
  {
diff --git a/src/pl/plpython/plpython.h b/src/pl/plpython/plpython.h
index ...53d25b7 .
*** a/src/pl/plpython/plpython.h
--- b/src/pl/plpython/plpython.h
***************
*** 0 ****
--- 1,40 ----
+ /*
+  * src/pl/plpython/plpython.h
+  */
+ #ifndef __PLPYTHON_H__
+ #define __PLPYTHON_H__
+ 
+ 
+ 
+ /*
+  * Rendezvous variable pattern for parsers exported from other extensions
+  *
+  * An extension providing parsres for type X should look up the type's OID and
+  * set a rendezvous variable using this pattern that points to a PLyParsers
+  * structure. PL/Python will then use these parsers for arguments with that
+  * OID.
+  */
+ #define PARSERS_VARIABLE_PATTERN "plpython_%u_parsers"
+ 
+ /*
+  * Types for parsres functions that other modules can export to transform
+  * Datums into PyObjects and back. The types need to be compatible with
+  * PLyObToDatumFunc and PLyDatumToObFunc, but we don't want to expose too much
+  * of plpython.c's guts here, so the first arguments is mandated to be a void
+  * pointer that should not be touched. An extension should know exactly what
+  * it's dealing with, so there's no need for it to look at anything contained
+  * in PLyTypeInfo, which is what gets passed here.
+  *
+  * The output parser also gets the type's typmod, which might actually be
+  * useful.
+  */
+ typedef PyObject *(*PLyParserIn) (void *, Datum);
+ typedef Datum (*PLyParserOut) (void *, int32, PyObject *);
+ 
+ typedef struct PLyParsers
+ {
+ 	PLyParserIn			in;
+ 	PLyParserOut		out;
+ } PLyParsers;
+ 
+ #endif   /* __PLPYTHON_H__ */

diff --git a/contrib/hstore/Makefile b/contrib/hstore/Makefile
index 1d533fd..fd85052 100644
*** a/contrib/hstore/Makefile
--- b/contrib/hstore/Makefile
***************
*** 1,8 ****
  # contrib/hstore/Makefile
  
  MODULE_big = hstore
  OBJS = hstore_io.o hstore_op.o hstore_gist.o hstore_gin.o hstore_compat.o \
! 	crc32.o
  
  DATA_built = hstore.sql
  DATA = uninstall_hstore.sql
--- 1,9 ----
  # contrib/hstore/Makefile
  
  MODULE_big = hstore
+ 
  OBJS = hstore_io.o hstore_op.o hstore_gist.o hstore_gin.o hstore_compat.o \
! 	hstore_plpython.o crc32.o
  
  DATA_built = hstore.sql
  DATA = uninstall_hstore.sql
*************** top_builddir = ../..
*** 18,20 ****
--- 19,28 ----
  include $(top_builddir)/src/Makefile.global
  include $(top_srcdir)/contrib/contrib-global.mk
  endif
+ 
+ ifeq ($(with_python), yes)
+ override CFLAGS += -I$(srcdir) -I$(top_builddir)/src/pl/plpython \
+ 			$(python_includespec) -DHSTORE_PLPYTHON_SUPPORT
+ SHLIB_LINK = $(python_libspec) $(python_additional_libs) \
+ 		$(filter -lintl,$(LIBS)) $(CPPFLAGS)
+ endif
diff --git a/contrib/hstore/expected/hstore.out b/contrib/hstore/expected/hstore.out
index 354fff2..049fdd5 100644
*** a/contrib/hstore/expected/hstore.out
--- b/contrib/hstore/expected/hstore.out
*************** select count(*) from testhstore where h
*** 1461,1463 ****
--- 1461,1502 ----
       1
  (1 row)
  
+ -- plpython integration
+ set plpython.hstore = 'public.hstore';
+ create language plpythonu;
+ create or replace function select_one(h hstore, idx text) returns text as $$
+ try:
+     return h.get(idx)
+ except AttributeError:
+     # h has not been transformed into a dict and is a string
+     return None
+ $$ language plpythonu;
+ select coalesce(select_one(h, 'node'), '<null>') as node from testhstore where select_one(h, 'line')::integer < 10;
+   node  
+ --------
+  AA
+  CBB
+  <null>
+  <null>
+  CBA
+  CBC
+  <null>
+  <null>
+  <null>
+ (9 rows)
+ 
+ reset plpython.hstore;
+ create or replace function select_one(h hstore, idx text) returns text as $$
+ try:
+     return h.get(idx)
+ except AttributeError:
+     # h has not been transformed into a dict and is a string
+     return None
+ $$ language plpythonu;
+ select coalesce(select_one(h, 'node'), '<null>') as node from testhstore where select_one(h, 'line')::integer < 10;
+  node 
+ ------
+ (0 rows)
+ 
+ drop function select_one(hstore, text);
+ drop language plpythonu;
diff --git a/contrib/hstore/expected/hstore_0.out b/contrib/hstore/expected/hstore_0.out
index ...af06337 .
*** a/contrib/hstore/expected/hstore_0.out
--- b/contrib/hstore/expected/hstore_0.out
***************
*** 0 ****
--- 1,1495 ----
+ --
+ -- first, define the datatype.  Turn off echoing so that expected file
+ -- does not depend on contents of hstore.sql.
+ --
+ SET client_min_messages = warning;
+ \set ECHO none
+ psql:hstore.sql:228: WARNING:  => is deprecated as an operator name
+ DETAIL:  This name may be disallowed altogether in future versions of PostgreSQL.
+ RESET client_min_messages;
+ set escape_string_warning=off;
+ --hstore;
+ select ''::hstore;
+  hstore 
+ --------
+  
+ (1 row)
+ 
+ select 'a=>b'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select ' a=>b'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select 'a =>b'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select 'a=>b '::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select 'a=> b'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select '"a"=>"b"'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select ' "a"=>"b"'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select '"a" =>"b"'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select '"a"=>"b" '::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select '"a"=> "b"'::hstore;
+   hstore  
+ ----------
+  "a"=>"b"
+ (1 row)
+ 
+ select 'aa=>bb'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select ' aa=>bb'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select 'aa =>bb'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select 'aa=>bb '::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select 'aa=> bb'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select '"aa"=>"bb"'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select ' "aa"=>"bb"'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select '"aa" =>"bb"'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select '"aa"=>"bb" '::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select '"aa"=> "bb"'::hstore;
+    hstore   
+ ------------
+  "aa"=>"bb"
+ (1 row)
+ 
+ select 'aa=>bb, cc=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>bb , cc=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>bb ,cc=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>bb, "cc"=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>bb , "cc"=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>bb ,"cc"=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>"bb", cc=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>"bb" , cc=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>"bb" ,cc=>dd'::hstore;
+          hstore         
+ ------------------------
+  "aa"=>"bb", "cc"=>"dd"
+ (1 row)
+ 
+ select 'aa=>null'::hstore;
+    hstore   
+ ------------
+  "aa"=>NULL
+ (1 row)
+ 
+ select 'aa=>NuLl'::hstore;
+    hstore   
+ ------------
+  "aa"=>NULL
+ (1 row)
+ 
+ select 'aa=>"NuLl"'::hstore;
+     hstore    
+ --------------
+  "aa"=>"NuLl"
+ (1 row)
+ 
+ select e'\\=a=>q=w'::hstore;
+    hstore    
+ -------------
+  "=a"=>"q=w"
+ (1 row)
+ 
+ select e'"=a"=>q\\=w'::hstore;
+    hstore    
+ -------------
+  "=a"=>"q=w"
+ (1 row)
+ 
+ select e'"\\"a"=>q>w'::hstore;
+     hstore    
+ --------------
+  "\"a"=>"q>w"
+ (1 row)
+ 
+ select e'\\"a=>q"w'::hstore;
+     hstore     
+ ---------------
+  "\"a"=>"q\"w"
+ (1 row)
+ 
+ select ''::hstore;
+  hstore 
+ --------
+  
+ (1 row)
+ 
+ select '	'::hstore;
+  hstore 
+ --------
+  
+ (1 row)
+ 
+ -- -> operator
+ select 'aa=>b, c=>d , b=>16'::hstore->'c';
+  ?column? 
+ ----------
+  d
+ (1 row)
+ 
+ select 'aa=>b, c=>d , b=>16'::hstore->'b';
+  ?column? 
+ ----------
+  16
+ (1 row)
+ 
+ select 'aa=>b, c=>d , b=>16'::hstore->'aa';
+  ?column? 
+ ----------
+  b
+ (1 row)
+ 
+ select ('aa=>b, c=>d , b=>16'::hstore->'gg') is null;
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select ('aa=>NULL, c=>d , b=>16'::hstore->'aa') is null;
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select ('aa=>"NULL", c=>d , b=>16'::hstore->'aa') is null;
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ -- -> array operator
+ select 'aa=>"NULL", c=>d , b=>16'::hstore -> ARRAY['aa','c'];
+   ?column?  
+ ------------
+  {"NULL",d}
+ (1 row)
+ 
+ select 'aa=>"NULL", c=>d , b=>16'::hstore -> ARRAY['c','aa'];
+   ?column?  
+ ------------
+  {d,"NULL"}
+ (1 row)
+ 
+ select 'aa=>NULL, c=>d , b=>16'::hstore -> ARRAY['aa','c',null];
+    ?column?    
+ ---------------
+  {NULL,d,NULL}
+ (1 row)
+ 
+ select 'aa=>1, c=>3, b=>2, d=>4'::hstore -> ARRAY[['b','d'],['aa','c']];
+    ?column?    
+ ---------------
+  {{2,4},{1,3}}
+ (1 row)
+ 
+ -- exists/defined
+ select exist('a=>NULL, b=>qq', 'a');
+  exist 
+ -------
+  t
+ (1 row)
+ 
+ select exist('a=>NULL, b=>qq', 'b');
+  exist 
+ -------
+  t
+ (1 row)
+ 
+ select exist('a=>NULL, b=>qq', 'c');
+  exist 
+ -------
+  f
+ (1 row)
+ 
+ select exist('a=>"NULL", b=>qq', 'a');
+  exist 
+ -------
+  t
+ (1 row)
+ 
+ select defined('a=>NULL, b=>qq', 'a');
+  defined 
+ ---------
+  f
+ (1 row)
+ 
+ select defined('a=>NULL, b=>qq', 'b');
+  defined 
+ ---------
+  t
+ (1 row)
+ 
+ select defined('a=>NULL, b=>qq', 'c');
+  defined 
+ ---------
+  f
+ (1 row)
+ 
+ select defined('a=>"NULL", b=>qq', 'a');
+  defined 
+ ---------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ? 'a';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ? 'b';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ? 'c';
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select hstore 'a=>"NULL", b=>qq' ? 'a';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?| ARRAY['a','b'];
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?| ARRAY['b','a'];
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?| ARRAY['c','a'];
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?| ARRAY['c','d'];
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?| '{}'::text[];
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?& ARRAY['a','b'];
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?& ARRAY['b','a'];
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?& ARRAY['c','a'];
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?& ARRAY['c','d'];
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select hstore 'a=>NULL, b=>qq' ?& '{}'::text[];
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- delete
+ select delete('a=>1 , b=>2, c=>3'::hstore, 'a');
+        delete       
+ --------------------
+  "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select delete('a=>null , b=>2, c=>3'::hstore, 'a');
+        delete       
+ --------------------
+  "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, 'b');
+        delete       
+ --------------------
+  "a"=>"1", "c"=>"3"
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, 'c');
+        delete       
+ --------------------
+  "a"=>"1", "b"=>"2"
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, 'd');
+             delete            
+ ------------------------------
+  "a"=>"1", "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - 'a'::text;
+       ?column?      
+ --------------------
+  "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>null , b=>2, c=>3'::hstore - 'a'::text;
+       ?column?      
+ --------------------
+  "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - 'b'::text;
+       ?column?      
+ --------------------
+  "a"=>"1", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - 'c'::text;
+       ?column?      
+ --------------------
+  "a"=>"1", "b"=>"2"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - 'd'::text;
+            ?column?           
+ ------------------------------
+  "a"=>"1", "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select pg_column_size('a=>1 , b=>2, c=>3'::hstore - 'b'::text)
+          = pg_column_size('a=>1, b=>2'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- delete (array)
+ select delete('a=>1 , b=>2, c=>3'::hstore, ARRAY['d','e']);
+             delete            
+ ------------------------------
+  "a"=>"1", "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, ARRAY['d','b']);
+        delete       
+ --------------------
+  "a"=>"1", "c"=>"3"
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, ARRAY['a','c']);
+   delete  
+ ----------
+  "b"=>"2"
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, ARRAY[['b'],['c'],['a']]);
+  delete 
+ --------
+  
+ (1 row)
+ 
+ select delete('a=>1 , b=>2, c=>3'::hstore, '{}'::text[]);
+             delete            
+ ------------------------------
+  "a"=>"1", "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - ARRAY['d','e'];
+            ?column?           
+ ------------------------------
+  "a"=>"1", "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - ARRAY['d','b'];
+       ?column?      
+ --------------------
+  "a"=>"1", "c"=>"3"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - ARRAY['a','c'];
+  ?column? 
+ ----------
+  "b"=>"2"
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - ARRAY[['b'],['c'],['a']];
+  ?column? 
+ ----------
+  
+ (1 row)
+ 
+ select 'a=>1 , b=>2, c=>3'::hstore - '{}'::text[];
+            ?column?           
+ ------------------------------
+  "a"=>"1", "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select pg_column_size('a=>1 , b=>2, c=>3'::hstore - ARRAY['a','c'])
+          = pg_column_size('b=>2'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size('a=>1 , b=>2, c=>3'::hstore - '{}'::text[])
+          = pg_column_size('a=>1, b=>2, c=>3'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- delete (hstore)
+ select delete('aa=>1 , b=>2, c=>3'::hstore, 'aa=>4, b=>2'::hstore);
+        delete        
+ ---------------------
+  "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select delete('aa=>1 , b=>2, c=>3'::hstore, 'aa=>NULL, c=>3'::hstore);
+        delete        
+ ---------------------
+  "b"=>"2", "aa"=>"1"
+ (1 row)
+ 
+ select delete('aa=>1 , b=>2, c=>3'::hstore, 'aa=>1, b=>2, c=>3'::hstore);
+  delete 
+ --------
+  
+ (1 row)
+ 
+ select delete('aa=>1 , b=>2, c=>3'::hstore, 'b=>2'::hstore);
+        delete        
+ ---------------------
+  "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select delete('aa=>1 , b=>2, c=>3'::hstore, ''::hstore);
+             delete             
+ -------------------------------
+  "b"=>"2", "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, c=>3'::hstore - 'aa=>4, b=>2'::hstore;
+       ?column?       
+ ---------------------
+  "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, c=>3'::hstore - 'aa=>NULL, c=>3'::hstore;
+       ?column?       
+ ---------------------
+  "b"=>"2", "aa"=>"1"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, c=>3'::hstore - 'aa=>1, b=>2, c=>3'::hstore;
+  ?column? 
+ ----------
+  
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, c=>3'::hstore - 'b=>2'::hstore;
+       ?column?       
+ ---------------------
+  "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, c=>3'::hstore - ''::hstore;
+            ?column?            
+ -------------------------------
+  "b"=>"2", "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select pg_column_size('a=>1 , b=>2, c=>3'::hstore - 'b=>2'::hstore)
+          = pg_column_size('a=>1, c=>3'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size('a=>1 , b=>2, c=>3'::hstore - ''::hstore)
+          = pg_column_size('a=>1, b=>2, c=>3'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- ||
+ select 'aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>f';
+                  ?column?                  
+ -------------------------------------------
+  "b"=>"g", "aa"=>"1", "cq"=>"l", "fg"=>"f"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, cq=>3'::hstore || 'aq=>l';
+                  ?column?                  
+ -------------------------------------------
+  "b"=>"2", "aa"=>"1", "aq"=>"l", "cq"=>"3"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, cq=>3'::hstore || 'aa=>l';
+             ?column?            
+ --------------------------------
+  "b"=>"2", "aa"=>"l", "cq"=>"3"
+ (1 row)
+ 
+ select 'aa=>1 , b=>2, cq=>3'::hstore || '';
+             ?column?            
+ --------------------------------
+  "b"=>"2", "aa"=>"1", "cq"=>"3"
+ (1 row)
+ 
+ select ''::hstore || 'cq=>l, b=>g, fg=>f';
+             ?column?            
+ --------------------------------
+  "b"=>"g", "cq"=>"l", "fg"=>"f"
+ (1 row)
+ 
+ select pg_column_size(''::hstore || ''::hstore) = pg_column_size(''::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size('aa=>1'::hstore || 'b=>2'::hstore)
+          = pg_column_size('aa=>1, b=>2'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size('aa=>1, b=>2'::hstore || ''::hstore)
+          = pg_column_size('aa=>1, b=>2'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size(''::hstore || 'aa=>1, b=>2'::hstore)
+          = pg_column_size('aa=>1, b=>2'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- =>
+ select 'a=>g, b=>c'::hstore || ( 'asd'=>'gf' );
+             ?column?             
+ ---------------------------------
+  "a"=>"g", "b"=>"c", "asd"=>"gf"
+ (1 row)
+ 
+ select 'a=>g, b=>c'::hstore || ( 'b'=>'gf' );
+       ?column?       
+ ---------------------
+  "a"=>"g", "b"=>"gf"
+ (1 row)
+ 
+ select 'a=>g, b=>c'::hstore || ( 'b'=>'NULL' );
+        ?column?        
+ -----------------------
+  "a"=>"g", "b"=>"NULL"
+ (1 row)
+ 
+ select 'a=>g, b=>c'::hstore || ( 'b'=>NULL );
+       ?column?       
+ ---------------------
+  "a"=>"g", "b"=>NULL
+ (1 row)
+ 
+ select ('a=>g, b=>c'::hstore || ( NULL=>'b' )) is null;
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size(('b'=>'gf'))
+          = pg_column_size('b=>gf'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size('a=>g, b=>c'::hstore || ('b'=>'gf'))
+          = pg_column_size('a=>g, b=>gf'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- slice()
+ select slice(hstore 'aa=>1, b=>2, c=>3', ARRAY['g','h','i']);
+  slice 
+ -------
+  
+ (1 row)
+ 
+ select slice(hstore 'aa=>1, b=>2, c=>3', ARRAY['c','b']);
+        slice        
+ --------------------
+  "b"=>"2", "c"=>"3"
+ (1 row)
+ 
+ select slice(hstore 'aa=>1, b=>2, c=>3', ARRAY['aa','b']);
+         slice        
+ ---------------------
+  "b"=>"2", "aa"=>"1"
+ (1 row)
+ 
+ select slice(hstore 'aa=>1, b=>2, c=>3', ARRAY['c','b','aa']);
+              slice             
+ -------------------------------
+  "b"=>"2", "c"=>"3", "aa"=>"1"
+ (1 row)
+ 
+ select pg_column_size(slice(hstore 'aa=>1, b=>2, c=>3', ARRAY['c','b']))
+          = pg_column_size('b=>2, c=>3'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select pg_column_size(slice(hstore 'aa=>1, b=>2, c=>3', ARRAY['c','b','aa']))
+          = pg_column_size('aa=>1, b=>2, c=>3'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- array input
+ select '{}'::text[]::hstore;
+  hstore 
+ --------
+  
+ (1 row)
+ 
+ select ARRAY['a','g','b','h','asd']::hstore;
+ ERROR:  array must have even number of elements
+ select ARRAY['a','g','b','h','asd','i']::hstore;
+              array              
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ select ARRAY[['a','g'],['b','h'],['asd','i']]::hstore;
+              array              
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ select ARRAY[['a','g','b'],['h','asd','i']]::hstore;
+ ERROR:  array must have two columns
+ select ARRAY[[['a','g'],['b','h'],['asd','i']]]::hstore;
+ ERROR:  wrong number of array subscripts
+ select hstore('{}'::text[]);
+  hstore 
+ --------
+  
+ (1 row)
+ 
+ select hstore(ARRAY['a','g','b','h','asd']);
+ ERROR:  array must have even number of elements
+ select hstore(ARRAY['a','g','b','h','asd','i']);
+              hstore             
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ select hstore(ARRAY[['a','g'],['b','h'],['asd','i']]);
+              hstore             
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ select hstore(ARRAY[['a','g','b'],['h','asd','i']]);
+ ERROR:  array must have two columns
+ select hstore(ARRAY[[['a','g'],['b','h'],['asd','i']]]);
+ ERROR:  wrong number of array subscripts
+ select hstore('[0:5]={a,g,b,h,asd,i}'::text[]);
+              hstore             
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ select hstore('[0:2][1:2]={{a,g},{b,h},{asd,i}}'::text[]);
+              hstore             
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ -- pairs of arrays
+ select hstore(ARRAY['a','b','asd'], ARRAY['g','h','i']);
+              hstore             
+ --------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>"i"
+ (1 row)
+ 
+ select hstore(ARRAY['a','b','asd'], ARRAY['g','h',NULL]);
+              hstore              
+ ---------------------------------
+  "a"=>"g", "b"=>"h", "asd"=>NULL
+ (1 row)
+ 
+ select hstore(ARRAY['z','y','x'], ARRAY['1','2','3']);
+             hstore            
+ ------------------------------
+  "x"=>"3", "y"=>"2", "z"=>"1"
+ (1 row)
+ 
+ select hstore(ARRAY['aaa','bb','c','d'], ARRAY[null::text,null,null,null]);
+                     hstore                     
+ -----------------------------------------------
+  "c"=>NULL, "d"=>NULL, "bb"=>NULL, "aaa"=>NULL
+ (1 row)
+ 
+ select hstore(ARRAY['aaa','bb','c','d'], null);
+                     hstore                     
+ -----------------------------------------------
+  "c"=>NULL, "d"=>NULL, "bb"=>NULL, "aaa"=>NULL
+ (1 row)
+ 
+ select quote_literal(hstore('{}'::text[], '{}'::text[]));
+  quote_literal 
+ ---------------
+  ''
+ (1 row)
+ 
+ select quote_literal(hstore('{}'::text[], null));
+  quote_literal 
+ ---------------
+  ''
+ (1 row)
+ 
+ select hstore(ARRAY['a'], '{}'::text[]);  -- error
+ ERROR:  arrays must have same bounds
+ select hstore('{}'::text[], ARRAY['a']);  -- error
+ ERROR:  arrays must have same bounds
+ select pg_column_size(hstore(ARRAY['a','b','asd'], ARRAY['g','h','i']))
+          = pg_column_size('a=>g, b=>h, asd=>i'::hstore);
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ -- records
+ select hstore(v) from (values (1, 'foo', 1.2, 3::float8)) v(a,b,c,d);
+                      hstore                     
+ ------------------------------------------------
+  "f1"=>"1", "f2"=>"foo", "f3"=>"1.2", "f4"=>"3"
+ (1 row)
+ 
+ create domain hstestdom1 as integer not null default 0;
+ create table testhstore0 (a integer, b text, c numeric, d float8);
+ create table testhstore1 (a integer, b text, c numeric, d float8, e hstestdom1);
+ insert into testhstore0 values (1, 'foo', 1.2, 3::float8);
+ insert into testhstore1 values (1, 'foo', 1.2, 3::float8);
+ select hstore(v) from testhstore1 v;
+                         hstore                        
+ ------------------------------------------------------
+  "a"=>"1", "b"=>"foo", "c"=>"1.2", "d"=>"3", "e"=>"0"
+ (1 row)
+ 
+ select hstore(null::testhstore0);
+                    hstore                   
+ --------------------------------------------
+  "a"=>NULL, "b"=>NULL, "c"=>NULL, "d"=>NULL
+ (1 row)
+ 
+ select hstore(null::testhstore1);
+                         hstore                         
+ -------------------------------------------------------
+  "a"=>NULL, "b"=>NULL, "c"=>NULL, "d"=>NULL, "e"=>NULL
+ (1 row)
+ 
+ select pg_column_size(hstore(v))
+          = pg_column_size('a=>1, b=>"foo", c=>"1.2", d=>"3", e=>"0"'::hstore)
+   from testhstore1 v;
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select populate_record(v, ('c' => '3.45')) from testhstore1 v;
+  populate_record  
+ ------------------
+  (1,foo,3.45,3,0)
+ (1 row)
+ 
+ select populate_record(v, ('d' => '3.45')) from testhstore1 v;
+   populate_record   
+ --------------------
+  (1,foo,1.2,3.45,0)
+ (1 row)
+ 
+ select populate_record(v, ('e' => '123')) from testhstore1 v;
+   populate_record  
+ -------------------
+  (1,foo,1.2,3,123)
+ (1 row)
+ 
+ select populate_record(v, ('e' => null)) from testhstore1 v;
+ ERROR:  domain hstestdom1 does not allow null values
+ select populate_record(v, ('c' => null)) from testhstore1 v;
+  populate_record 
+ -----------------
+  (1,foo,,3,0)
+ (1 row)
+ 
+ select populate_record(v, ('b' => 'foo') || ('a' => '123')) from testhstore1 v;
+   populate_record  
+ -------------------
+  (123,foo,1.2,3,0)
+ (1 row)
+ 
+ select populate_record(v, ('b' => 'foo') || ('e' => null)) from testhstore0 v;
+  populate_record 
+ -----------------
+  (1,foo,1.2,3)
+ (1 row)
+ 
+ select populate_record(v, ('b' => 'foo') || ('e' => null)) from testhstore1 v;
+ ERROR:  domain hstestdom1 does not allow null values
+ select populate_record(v, '') from testhstore0 v;
+  populate_record 
+ -----------------
+  (1,foo,1.2,3)
+ (1 row)
+ 
+ select populate_record(v, '') from testhstore1 v;
+  populate_record 
+ -----------------
+  (1,foo,1.2,3,0)
+ (1 row)
+ 
+ select populate_record(null::testhstore1, ('c' => '3.45') || ('a' => '123'));
+ ERROR:  domain hstestdom1 does not allow null values
+ select populate_record(null::testhstore1, ('c' => '3.45') || ('e' => '123'));
+  populate_record 
+ -----------------
+  (,,3.45,,123)
+ (1 row)
+ 
+ select populate_record(null::testhstore0, '');
+  populate_record 
+ -----------------
+  (,,,)
+ (1 row)
+ 
+ select populate_record(null::testhstore1, '');
+ ERROR:  domain hstestdom1 does not allow null values
+ select v #= ('c' => '3.45') from testhstore1 v;
+      ?column?     
+ ------------------
+  (1,foo,3.45,3,0)
+ (1 row)
+ 
+ select v #= ('d' => '3.45') from testhstore1 v;
+       ?column?      
+ --------------------
+  (1,foo,1.2,3.45,0)
+ (1 row)
+ 
+ select v #= ('e' => '123') from testhstore1 v;
+      ?column?      
+ -------------------
+  (1,foo,1.2,3,123)
+ (1 row)
+ 
+ select v #= ('c' => null) from testhstore1 v;
+    ?column?   
+ --------------
+  (1,foo,,3,0)
+ (1 row)
+ 
+ select v #= ('e' => null) from testhstore0 v;
+    ?column?    
+ ---------------
+  (1,foo,1.2,3)
+ (1 row)
+ 
+ select v #= ('e' => null) from testhstore1 v;
+ ERROR:  domain hstestdom1 does not allow null values
+ select v #= (('b' => 'foo') || ('a' => '123')) from testhstore1 v;
+      ?column?      
+ -------------------
+  (123,foo,1.2,3,0)
+ (1 row)
+ 
+ select v #= (('b' => 'foo') || ('e' => '123')) from testhstore1 v;
+      ?column?      
+ -------------------
+  (1,foo,1.2,3,123)
+ (1 row)
+ 
+ select v #= hstore '' from testhstore0 v;
+    ?column?    
+ ---------------
+  (1,foo,1.2,3)
+ (1 row)
+ 
+ select v #= hstore '' from testhstore1 v;
+     ?column?     
+ -----------------
+  (1,foo,1.2,3,0)
+ (1 row)
+ 
+ select null::testhstore1 #= (('c' => '3.45') || ('a' => '123'));
+ ERROR:  domain hstestdom1 does not allow null values
+ select null::testhstore1 #= (('c' => '3.45') || ('e' => '123'));
+    ?column?    
+ ---------------
+  (,,3.45,,123)
+ (1 row)
+ 
+ select null::testhstore0 #= hstore '';
+  ?column? 
+ ----------
+  (,,,)
+ (1 row)
+ 
+ select null::testhstore1 #= hstore '';
+ ERROR:  domain hstestdom1 does not allow null values
+ select v #= h from testhstore1 v, (values (hstore 'a=>123',1),('b=>foo,c=>3.21',2),('a=>null',3),('e=>123',4),('f=>blah',5)) x(h,i) order by i;
+      ?column?      
+ -------------------
+  (123,foo,1.2,3,0)
+  (1,foo,3.21,3,0)
+  (,foo,1.2,3,0)
+  (1,foo,1.2,3,123)
+  (1,foo,1.2,3,0)
+ (5 rows)
+ 
+ -- keys/values
+ select akeys('aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>f');
+     akeys     
+ --------------
+  {b,aa,cq,fg}
+ (1 row)
+ 
+ select akeys('""=>1');
+  akeys 
+ -------
+  {""}
+ (1 row)
+ 
+ select akeys('');
+  akeys 
+ -------
+  {}
+ (1 row)
+ 
+ select avals('aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>f');
+    avals   
+ -----------
+  {g,1,l,f}
+ (1 row)
+ 
+ select avals('aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>NULL');
+     avals     
+ --------------
+  {g,1,l,NULL}
+ (1 row)
+ 
+ select avals('""=>1');
+  avals 
+ -------
+  {1}
+ (1 row)
+ 
+ select avals('');
+  avals 
+ -------
+  {}
+ (1 row)
+ 
+ select hstore_to_array('aa=>1, cq=>l, b=>g, fg=>NULL'::hstore);
+      hstore_to_array     
+ -------------------------
+  {b,g,aa,1,cq,l,fg,NULL}
+ (1 row)
+ 
+ select %% 'aa=>1, cq=>l, b=>g, fg=>NULL';
+         ?column?         
+ -------------------------
+  {b,g,aa,1,cq,l,fg,NULL}
+ (1 row)
+ 
+ select hstore_to_matrix('aa=>1, cq=>l, b=>g, fg=>NULL'::hstore);
+         hstore_to_matrix         
+ ---------------------------------
+  {{b,g},{aa,1},{cq,l},{fg,NULL}}
+ (1 row)
+ 
+ select %# 'aa=>1, cq=>l, b=>g, fg=>NULL';
+             ?column?             
+ ---------------------------------
+  {{b,g},{aa,1},{cq,l},{fg,NULL}}
+ (1 row)
+ 
+ select * from skeys('aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>f');
+  skeys 
+ -------
+  b
+  aa
+  cq
+  fg
+ (4 rows)
+ 
+ select * from skeys('""=>1');
+  skeys 
+ -------
+  
+ (1 row)
+ 
+ select * from skeys('');
+  skeys 
+ -------
+ (0 rows)
+ 
+ select * from svals('aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>f');
+  svals 
+ -------
+  g
+  1
+  l
+  f
+ (4 rows)
+ 
+ select *, svals is null from svals('aa=>1 , b=>2, cq=>3'::hstore || 'cq=>l, b=>g, fg=>NULL');
+  svals | ?column? 
+ -------+----------
+  g     | f
+  1     | f
+  l     | f
+        | t
+ (4 rows)
+ 
+ select * from svals('""=>1');
+  svals 
+ -------
+  1
+ (1 row)
+ 
+ select * from svals('');
+  svals 
+ -------
+ (0 rows)
+ 
+ select * from each('aaa=>bq, b=>NULL, ""=>1 ');
+  key | value 
+ -----+-------
+      | 1
+  b   | 
+  aaa | bq
+ (3 rows)
+ 
+ -- @>
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'a=>b';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'a=>b, c=>NULL';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'a=>b, g=>NULL';
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'g=>NULL';
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'a=>c';
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'a=>b';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
+ select 'a=>b, b=>1, c=>NULL'::hstore @> 'a=>b, c=>q';
+  ?column? 
+ ----------
+  f
+ (1 row)
+ 
+ CREATE TABLE testhstore (h hstore);
+ \copy testhstore from 'data/hstore.data'
+ select count(*) from testhstore where h @> 'wait=>NULL';
+  count 
+ -------
+      1
+ (1 row)
+ 
+ select count(*) from testhstore where h @> 'wait=>CC';
+  count 
+ -------
+     15
+ (1 row)
+ 
+ select count(*) from testhstore where h @> 'wait=>CC, public=>t';
+  count 
+ -------
+      2
+ (1 row)
+ 
+ select count(*) from testhstore where h ? 'public';
+  count 
+ -------
+    194
+ (1 row)
+ 
+ select count(*) from testhstore where h ?| ARRAY['public','disabled'];
+  count 
+ -------
+    337
+ (1 row)
+ 
+ select count(*) from testhstore where h ?& ARRAY['public','disabled'];
+  count 
+ -------
+     42
+ (1 row)
+ 
+ create index hidx on testhstore using gist(h);
+ set enable_seqscan=off;
+ select count(*) from testhstore where h @> 'wait=>NULL';
+  count 
+ -------
+      1
+ (1 row)
+ 
+ select count(*) from testhstore where h @> 'wait=>CC';
+  count 
+ -------
+     15
+ (1 row)
+ 
+ select count(*) from testhstore where h @> 'wait=>CC, public=>t';
+  count 
+ -------
+      2
+ (1 row)
+ 
+ select count(*) from testhstore where h ? 'public';
+  count 
+ -------
+    194
+ (1 row)
+ 
+ select count(*) from testhstore where h ?| ARRAY['public','disabled'];
+  count 
+ -------
+    337
+ (1 row)
+ 
+ select count(*) from testhstore where h ?& ARRAY['public','disabled'];
+  count 
+ -------
+     42
+ (1 row)
+ 
+ drop index hidx;
+ create index hidx on testhstore using gin (h);
+ set enable_seqscan=off;
+ select count(*) from testhstore where h @> 'wait=>NULL';
+  count 
+ -------
+      1
+ (1 row)
+ 
+ select count(*) from testhstore where h @> 'wait=>CC';
+  count 
+ -------
+     15
+ (1 row)
+ 
+ select count(*) from testhstore where h @> 'wait=>CC, public=>t';
+  count 
+ -------
+      2
+ (1 row)
+ 
+ select count(*) from testhstore where h ? 'public';
+  count 
+ -------
+    194
+ (1 row)
+ 
+ select count(*) from testhstore where h ?| ARRAY['public','disabled'];
+  count 
+ -------
+    337
+ (1 row)
+ 
+ select count(*) from testhstore where h ?& ARRAY['public','disabled'];
+  count 
+ -------
+     42
+ (1 row)
+ 
+ select count(*) from (select (each(h)).key from testhstore) as wow ;
+  count 
+ -------
+   4781
+ (1 row)
+ 
+ select key, count(*) from (select (each(h)).key from testhstore) as wow group by key order by count desc, key;
+     key    | count 
+ -----------+-------
+  line      |   884
+  query     |   207
+  pos       |   203
+  node      |   202
+  space     |   197
+  status    |   195
+  public    |   194
+  title     |   190
+  wait      |   190
+  org       |   189
+  user      |   189
+  coauthors |   188
+  disabled  |   185
+  indexed   |   184
+  cleaned   |   180
+  bad       |   179
+  date      |   179
+  world     |   176
+  state     |   172
+  subtitle  |   169
+  auth      |   168
+  abstract  |   161
+ (22 rows)
+ 
+ -- sort/hash
+ select count(distinct h) from testhstore;
+  count 
+ -------
+    885
+ (1 row)
+ 
+ set enable_hashagg = false;
+ select count(*) from (select h from (select * from testhstore union all select * from testhstore) hs group by h) hs2;
+  count 
+ -------
+    885
+ (1 row)
+ 
+ set enable_hashagg = true;
+ set enable_sort = false;
+ select count(*) from (select h from (select * from testhstore union all select * from testhstore) hs group by h) hs2;
+  count 
+ -------
+    885
+ (1 row)
+ 
+ select distinct * from (values (hstore '' || ''),('')) v(h);
+  h 
+ ---
+  
+ (1 row)
+ 
+ set enable_sort = true;
+ -- btree
+ drop index hidx;
+ create index hidx on testhstore using btree (h);
+ set enable_seqscan=off;
+ select count(*) from testhstore where h #># 'p=>1';
+  count 
+ -------
+    125
+ (1 row)
+ 
+ select count(*) from testhstore where h = 'pos=>98, line=>371, node=>CBA, indexed=>t';
+  count 
+ -------
+      1
+ (1 row)
+ 
+ -- plpython integration
+ set plpython.hstore = 'public.hstore';
+ ERROR:  unrecognized configuration parameter "plpython.hstore"
+ create language plpythonu;
+ create or replace function select_one(h hstore, idx text) returns text as $$
+ try:
+     return h.get(idx)
+ except AttributeError:
+     # h has not been transformed into a dict and is a string
+     return None
+ $$ language plpythonu;
+ select coalesce(select_one(h, 'node'), '<null>') as node from testhstore where select_one(h, 'line')::integer < 10;
+  node 
+ ------
+ (0 rows)
+ 
+ reset plpython.hstore;
+ ERROR:  unrecognized configuration parameter "plpython.hstore"
+ create or replace function select_one(h hstore, idx text) returns text as $$
+ try:
+     return h.get(idx)
+ except AttributeError:
+     # h has not been transformed into a dict and is a string
+     return None
+ $$ language plpythonu;
+ select coalesce(select_one(h, 'node'), '<null>') as node from testhstore where select_one(h, 'line')::integer < 10;
+  node 
+ ------
+ (0 rows)
+ 
+ drop function select_one(hstore, text);
+ drop language plpythonu;
diff --git a/contrib/hstore/hstore.h b/contrib/hstore/hstore.h
index 8906397..6edfc70 100644
*** a/contrib/hstore/hstore.h
--- b/contrib/hstore/hstore.h
*************** extern Pairs *hstoreArrayToPairs(ArrayTy
*** 174,179 ****
--- 174,182 ----
  #define HStoreExistsAllStrategyNumber	11
  #define HStoreOldContainsStrategyNumber 13		/* backwards compatibility */
  
+ /* PL/Python support */
+ extern void hstore_plpython_init(void);
+ 
  /*
   * defining HSTORE_POLLUTE_NAMESPACE=0 will prevent use of old function names;
   * for now, we default to on for the benefit of people restoring old dumps
diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 0d6f0b6..92c8db9 100644
*** a/contrib/hstore/hstore_io.c
--- b/contrib/hstore/hstore_io.c
*************** PG_MODULE_MAGIC;
*** 20,25 ****
--- 20,26 ----
  /* old names for C functions */
  HSTORE_POLLUTE(hstore_from_text, tconvert);
  
+ void _PG_init(void);
  
  typedef struct
  {
*************** hstore_send(PG_FUNCTION_ARGS)
*** 1211,1213 ****
--- 1212,1220 ----
  
  	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
  }
+ 
+ void
+ _PG_init(void)
+ {
+ 	hstore_plpython_init();
+ }
diff --git a/contrib/hstore/hstore_plpython.c b/contrib/hstore/hstore_plpython.c
index ...4bcdd83 .
*** a/contrib/hstore/hstore_plpython.c
--- b/contrib/hstore/hstore_plpython.c
***************
*** 0 ****
--- 1,247 ----
+ /*
+  * contrib/src/hstore_plpython.c
+  *
+  * bidirectional transformation between hstores and Python dictionary objects
+  */
+ 
+ /* Only build if PL/Python support is needed */
+ #if defined(HSTORE_PLPYTHON_SUPPORT)
+ 
+ #if defined(_MSC_VER) && defined(_DEBUG)
+ /* Python uses #pragma to bring in a non-default libpython on VC++ if
+  * _DEBUG is defined */
+ #undef _DEBUG
+ /* Also hide away errcode, since we load Python.h before postgres.h */
+ #define errcode __msvc_errcode
+ #include <Python.h>
+ #undef errcode
+ #define _DEBUG
+ #elif defined (_MSC_VER)
+ #define errcode __msvc_errcode
+ #include <Python.h>
+ #undef errcode
+ #else
+ #include <Python.h>
+ #endif
+ 
+ #include "postgres.h"
+ #include "utils/guc.h"
+ #include "utils/builtins.h"
+ #include "utils/syscache.h"
+ #include "catalog/namespace.h"
+ 
+ #include "plpython.h"
+ #include "hstore.h"
+ 
+ static Oid get_hstore_oid(const char *name);
+ static void set_hstore_parsers(Oid);
+ 
+ static PyObject *hstore_to_dict(void *, Datum);
+ static Datum dict_to_hstore(void *, int32, PyObject *);
+ 
+ /* GUC variables */
+ 
+ static char *hstore_name;
+ 
+ /* Previous hstore OID */
+ 
+ static Oid previous;
+ 
+ PLyParsers parsers;
+ 
+ static PyObject *
+ hstore_to_dict(void *ignored, Datum d)
+ {
+ 	HStore		*hstore = DatumGetHStoreP(d);
+     char        *base;
+     HEntry      *entries;
+     int          count;
+     int          i;
+     PyObject    *ret;
+ 
+ 	base = STRPTR(hstore);
+     entries = ARRPTR(hstore);
+ 
+     ret = PyDict_New();
+ 
+     count = HS_COUNT(hstore);
+ 
+     for (i = 0; i < count; i++)
+ 	{
+             PyObject *key, *val;
+ 
+             key = PyString_FromStringAndSize(HS_KEY(entries, base, i),
+                                              HS_KEYLEN(entries, i));
+             if (HS_VALISNULL(entries, i)) {
+                 Py_INCREF(Py_None);
+                 val = Py_None;
+             }
+             else {
+                 val = PyString_FromStringAndSize(HS_VAL(entries, base, i),
+                                                  HS_VALLEN(entries, i));
+             }
+ 
+             PyDict_SetItem(ret, key, val);
+         }
+ 
+     return ret;
+ }
+ 
+ static Datum
+ dict_to_hstore(void *ignored, int32 typmod, PyObject *dict)
+ {
+     HStore      *hstore;
+     int          pcount;
+ 	Pairs		*pairs;
+ 	PyObject	*key;
+ 	PyObject	*value;
+ 	Py_ssize_t	 pos;
+ 	char		*keys;
+ 	char		*vals;
+ 	int			 keylen;
+ 	int			 vallen;
+ 	int			 buflen;
+ 	int			 i;
+ 
+ 	if (!PyDict_Check(dict))
+ 		ereport(ERROR,
+ 				(errmsg("hstores can only be constructed "
+ 						"from Python dictionaries")));
+ 
+ 	pcount = PyDict_Size(dict);
+ 	pairs = palloc(pcount * sizeof(Pairs));
+ 	pos = i = 0;
+ 	/* loop over the dictionary, creating a Pair for each key/value pair */
+ 	while (PyDict_Next(dict, &pos, &key, &value)) {
+ 		if (!PyString_Check(key))
+ 			elog(ERROR, "hstore keys have to be strings");
+ 
+ 		PyString_AsStringAndSize(key, &keys, &keylen);
+ 
+ 		if (strlen(keys) != keylen)
+ 			elog(ERROR, "hstore keys cannot contain NUL bytes");
+ 
+ 		pairs[i].key = pstrdup(keys);
+ 		pairs[i].keylen = hstoreCheckKeyLen(keylen);
+ 		pairs[i].needfree = true;
+ 
+ 		if (value == Py_None) {
+ 			pairs[i].val = NULL;
+ 			pairs[i].vallen = 0;
+ 			pairs[i].isnull = true;
+ 		}
+ 		else {
+ 			if (!PyString_Check(value))
+ 				elog(ERROR, "hstore values have to be strings");
+ 
+ 			PyString_AsStringAndSize(value, &vals, &vallen);
+ 
+ 			if (strlen(vals) != vallen)
+ 				elog(ERROR, "hstore values cannot contain NUL bytes");
+ 
+ 			pairs[i].val = pstrdup(vals);
+ 			pairs[i].vallen = hstoreCheckValLen(vallen);
+ 			pairs[i].isnull = false;
+ 		}
+ 
+ 		i++;
+ 	}
+ 	pcount = hstoreUniquePairs(pairs, pcount, &buflen);
+ 	hstore = hstorePairs(pairs, pcount, buflen);
+ 
+ 	return PointerGetDatum(hstore);
+ }
+ 
+ static const char *
+ recheck_hstore_oid(const char *newvalue, bool doit, GucSource source)
+ {
+ 	Oid	hstore_oid;
+ 
+ 	hstore_oid = get_hstore_oid(newvalue);
+ 
+ 	if (*newvalue && !OidIsValid(hstore_oid))
+ 		return NULL;
+ 
+ 	if (doit)
+ 		set_hstore_parsers(hstore_oid);
+ 
+ 	return newvalue;
+ }
+ 
+ void
+ hstore_plpython_init(void)
+ {
+ 	DefineCustomStringVariable("plpython.hstore",
+ 	  "The fully qualified name of the hstore type.",
+ 							   NULL,
+ 							   &hstore_name,
+ 							   "",
+ 							   PGC_SUSET,
+ 							   0,
+ 							   recheck_hstore_oid,
+ 							   NULL);
+ 
+ 	EmitWarningsOnPlaceholders("plpython");
+ 
+ 	previous = InvalidOid;
+ 	parsers.in = hstore_to_dict;
+ 	parsers.out = dict_to_hstore;
+ 
+ 	if (hstore_name && *hstore_name)
+ 		recheck_hstore_oid(hstore_name, true, PGC_S_FILE);
+ }
+ 
+ static Oid
+ get_hstore_oid(const char *name)
+ {
+ 	text		*text_name;
+ 	List		*hstore_name;
+ 	char		*type_name;
+ 	Oid			 type_namespace;
+ 	Oid			 typoid;
+ 
+ 	Assert(name != NULL);
+ 
+ 	if (!(*name))
+ 		return InvalidOid;
+ 
+ 	text_name = cstring_to_text(name);
+ 	hstore_name = textToQualifiedNameList(text_name);
+ 	pfree(text_name);
+ 
+ 	type_namespace = QualifiedNameGetCreationNamespace(hstore_name, &type_name);
+ 
+ 	typoid = GetSysCacheOid2(TYPENAMENSP,
+ 							 CStringGetDatum(type_name),
+ 							 ObjectIdGetDatum(type_namespace));
+ 
+ 	return typoid;
+ }
+ 
+ static void
+ set_hstore_parsers(Oid hstore_oid)
+ {
+ 	char		 name[NAMEDATALEN];
+ 
+ 	if (OidIsValid(previous))
+ 	{
+ 		snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, previous);
+ 		*find_rendezvous_variable(name) = NULL;
+ 	}
+ 
+ 	if (OidIsValid(hstore_oid))
+ 	{
+ 		snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, hstore_oid);
+ 		*find_rendezvous_variable(name) = &parsers;
+ 		previous = hstore_oid;
+ 	}
+ }
+ 
+ #else	/* !defined(HSTORE_PLPYTHON_SUPPORT) */
+ 
+ extern void hstore_plpython_init(void);
+ 
+ void
+ hstore_plpython_init(void) {};
+ 
+ #endif	/* defined(HSTORE_PLPYTHON_SUPPORT) */
diff --git a/contrib/hstore/sql/hstore.sql b/contrib/hstore/sql/hstore.sql
index 58a7967..065e9a1 100644
*** a/contrib/hstore/sql/hstore.sql
--- b/contrib/hstore/sql/hstore.sql
*************** set enable_seqscan=off;
*** 338,340 ****
--- 338,369 ----
  
  select count(*) from testhstore where h #># 'p=>1';
  select count(*) from testhstore where h = 'pos=>98, line=>371, node=>CBA, indexed=>t';
+ 
+ -- plpython integration
+ set plpython.hstore = 'public.hstore';
+ create language plpythonu;
+ 
+ create or replace function select_one(h hstore, idx text) returns text as $$
+ try:
+     return h.get(idx)
+ except AttributeError:
+     # h has not been transformed into a dict and is a string
+     return None
+ $$ language plpythonu;
+ 
+ select coalesce(select_one(h, 'node'), '<null>') as node from testhstore where select_one(h, 'line')::integer < 10;
+ 
+ reset plpython.hstore;
+ 
+ create or replace function select_one(h hstore, idx text) returns text as $$
+ try:
+     return h.get(idx)
+ except AttributeError:
+     # h has not been transformed into a dict and is a string
+     return None
+ $$ language plpythonu;
+ 
+ select coalesce(select_one(h, 'node'), '<null>') as node from testhstore where select_one(h, 'line')::integer < 10;
+ 
+ drop function select_one(hstore, text);
+ drop language plpythonu;
diff --git a/src/pl/plpython/plpython.c b/src/pl/plpython/plpython.c
index fff7de7..2ed06f4 100644
*** a/src/pl/plpython/plpython.c
--- b/src/pl/plpython/plpython.c
*************** typedef int Py_ssize_t;
*** 90,95 ****
--- 90,97 ----
  #include <fcntl.h>
  
  /* postgreSQL stuff */
+ #include "plpython.h"
+ 
  #include "catalog/pg_proc.h"
  #include "catalog/pg_type.h"
  #include "commands/trigger.h"
*************** static PyObject *PLyList_FromArray(PLyDa
*** 358,363 ****
--- 360,368 ----
  
  static PyObject *PLyDict_FromTuple(PLyTypeInfo *, HeapTuple, TupleDesc);
  
+ static PLyParserIn PLy_get_custom_input_function(Oid oid);
+ static PLyParserOut PLy_get_custom_output_function(Oid oid);
+ 
  static Datum PLyObject_ToBool(PLyObToDatum *, int32, PyObject *);
  static Datum PLyObject_ToBytea(PLyObToDatum *, int32, PyObject *);
  static Datum PLyObject_ToDatum(PLyObToDatum *, int32, PyObject *);
*************** PLy_output_datum_func2(PLyObToDatum *arg
*** 1819,1824 ****
--- 1824,1830 ----
  {
  	Form_pg_type typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
  	Oid			element_type;
+ 	Oid			argument_type;
  
  	perm_fmgr_info(typeStruct->typinput, &arg->typfunc);
  	arg->typoid = HeapTupleGetOid(typeTup);
*************** PLy_output_datum_func2(PLyObToDatum *arg
*** 1826,1837 ****
  	arg->typbyval = typeStruct->typbyval;
  
  	element_type = get_element_type(arg->typoid);
  
  	/*
  	 * Select a conversion function to convert Python objects to PostgreSQL
  	 * datums.	Most data types can go through the generic function.
  	 */
! 	switch (getBaseType(element_type ? element_type : arg->typoid))
  	{
  		case BOOLOID:
  			arg->func = PLyObject_ToBool;
--- 1832,1844 ----
  	arg->typbyval = typeStruct->typbyval;
  
  	element_type = get_element_type(arg->typoid);
+ 	argument_type = getBaseType(element_type ? element_type : arg->typoid);
  
  	/*
  	 * Select a conversion function to convert Python objects to PostgreSQL
  	 * datums.	Most data types can go through the generic function.
  	 */
! 	switch (argument_type)
  	{
  		case BOOLOID:
  			arg->func = PLyObject_ToBool;
*************** PLy_output_datum_func2(PLyObToDatum *arg
*** 1840,1846 ****
  			arg->func = PLyObject_ToBytea;
  			break;
  		default:
! 			arg->func = PLyObject_ToDatum;
  			break;
  	}
  
--- 1847,1859 ----
  			arg->func = PLyObject_ToBytea;
  			break;
  		default:
! 			/* Last ditch effort of finding a rendezvous variable pointing to
! 			 * a parser function, useful for extension modules plugging in
! 			 * their own parsers
! 			 */
! 			arg->func = (PLyObToDatumFunc) PLy_get_custom_output_function(argument_type);
! 			if (arg->func == NULL)
! 				arg->func = PLyObject_ToDatum;
  			break;
  	}
  
*************** PLy_input_datum_func2(PLyDatumToOb *arg,
*** 1882,1887 ****
--- 1895,1901 ----
  {
  	Form_pg_type typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
  	Oid			element_type = get_element_type(typeOid);
+ 	Oid			argument_type;
  
  	/* Get the type's conversion information */
  	perm_fmgr_info(typeStruct->typoutput, &arg->typfunc);
*************** PLy_input_datum_func2(PLyDatumToOb *arg,
*** 1891,1898 ****
  	arg->typlen = typeStruct->typlen;
  	arg->typalign = typeStruct->typalign;
  
  	/* Determine which kind of Python object we will convert to */
! 	switch (getBaseType(element_type ? element_type : typeOid))
  	{
  		case BOOLOID:
  			arg->func = PLyBool_FromBool;
--- 1905,1914 ----
  	arg->typlen = typeStruct->typlen;
  	arg->typalign = typeStruct->typalign;
  
+ 	argument_type = getBaseType(element_type ? element_type : typeOid);
+ 
  	/* Determine which kind of Python object we will convert to */
! 	switch (argument_type)
  	{
  		case BOOLOID:
  			arg->func = PLyBool_FromBool;
*************** PLy_input_datum_func2(PLyDatumToOb *arg,
*** 1919,1925 ****
  			arg->func = PLyBytes_FromBytea;
  			break;
  		default:
! 			arg->func = PLyString_FromDatum;
  			break;
  	}
  
--- 1935,1947 ----
  			arg->func = PLyBytes_FromBytea;
  			break;
  		default:
! 			/* Last ditch effort of finding a rendezvous variable pointing to
! 			 * a parser function, useful for extension modules plugging in
! 			 * their own parsers
! 			 */
! 			arg->func = (PLyDatumToObFunc) PLy_get_custom_input_function(argument_type);
! 			if (arg->func == NULL)
! 				arg->func = PLyString_FromDatum;
  			break;
  	}
  
*************** PLy_typeinfo_dealloc(PLyTypeInfo *arg)
*** 1960,1965 ****
--- 1982,2021 ----
  	}
  }
  
+ /*
+  * Getting the parser functions from a rendezvous variable set by another
+  * extension.
+  */
+ static PLyParserIn
+ PLy_get_custom_input_function(Oid oid)
+ {
+ 	PLyParsers	*parsers;
+ 	char		 name[NAMEDATALEN];
+ 
+ 	snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, oid);
+ 	parsers = *find_rendezvous_variable(name);
+ 
+ 	if (parsers == NULL)
+ 		return NULL;
+ 
+ 	return parsers->in;
+ }
+ 
+ static PLyParserOut
+ PLy_get_custom_output_function(Oid oid)
+ {
+ 	PLyParsers	*parsers;
+ 	char		 name[NAMEDATALEN];
+ 
+ 	snprintf(name, NAMEDATALEN, PARSERS_VARIABLE_PATTERN, oid);
+ 	parsers = *find_rendezvous_variable(name);
+ 
+ 	if (parsers == NULL)
+ 		return NULL;
+ 
+ 	return parsers->out;
+ }
+ 
  static PyObject *
  PLyBool_FromBool(PLyDatumToOb *arg, Datum d)
  {
diff --git a/src/pl/plpython/plpython.h b/src/pl/plpython/plpython.h
index ...63c40c5 .
*** a/src/pl/plpython/plpython.h
--- b/src/pl/plpython/plpython.h
***************
*** 0 ****
--- 1,40 ----
+ /*
+  * src/pl/plpython/plpython.h
+  */
+ #ifndef __PLPYTHON_H__
+ #define __PLPYTHON_H__
+ 
+ 
+ 
+ /*
+  * Rendezvous variable pattern for parsers exported from other extensions
+  *
+  * An extension providing parsres for type X should look up the type's OID and
+  * set a rendezvous variable using this pattern that points to a PLyParsers
+  * structure. PL/Python will then use these parsers for arguments with that
+  * OID.
+  */
+ #define PARSERS_VARIABLE_PATTERN "plpython_%u_parsers"
+ 
+ /*
+  * Types for parsers functions that other modules can export to transform
+  * Datums into PyObjects and back. The types need to be compatible with
+  * PLyObToDatumFunc and PLyDatumToObFunc, but we don't want to expose too much
+  * of plpython.c's guts here, so the first arguments is mandated to be a void
+  * pointer that should not be touched. An extension should know exactly what
+  * it's dealing with, so there's no need for it to look at anything contained
+  * in PLyTypeInfo, which is what gets passed here.
+  *
+  * The output parser also gets the type's typmod, which might actually be
+  * useful.
+  */
+ typedef PyObject *(*PLyParserIn) (void *, Datum);
+ typedef Datum (*PLyParserOut) (void *, int32, PyObject *);
+ 
+ typedef struct PLyParsers
+ {
+ 	PLyParserIn			in;
+ 	PLyParserOut		out;
+ } PLyParsers;
+ 
+ #endif   /* __PLPYTHON_H__ */