Here is an implementation of the
information_schema.parameters.parameter_default column.
I ended up writing a C function to decode the whole thing from the
system catalogs, because it was too complicated in SQL, so I abandoned
the approach discussed in [0].
[0]:
http://archives.postgresql.org/message-id/1356092400.25658.6.ca...@vanquo.pezone.net
diff --git a/doc/src/sgml/information_schema.sgml b/doc/src/sgml/information_schema.sgml
index ddbc56c..4fa4ab8 100644
--- a/doc/src/sgml/information_schema.sgml
+++ b/doc/src/sgml/information_schema.sgml
@@ -3323,6 +3323,15 @@ <title><literal>parameters</literal> Columns</title>
in future versions.)
</entry>
</row>
+
+ <row>
+ <entry><literal>parameter_default</literal></entry>
+ <entry><type>character_data</type></entry>
+ <entry>
+ The default expression of the parameter, or null if none or if the
+ function is not owned by a currently enabled role.
+ </entry>
+ </row>
</tbody>
</tgroup>
</table>
diff --git a/src/backend/catalog/information_schema.sql b/src/backend/catalog/information_schema.sql
index 2307586..82d686a 100644
--- a/src/backend/catalog/information_schema.sql
+++ b/src/backend/catalog/information_schema.sql
@@ -1132,10 +1132,15 @@ CREATE VIEW parameters AS
CAST(null AS sql_identifier) AS scope_schema,
CAST(null AS sql_identifier) AS scope_name,
CAST(null AS cardinal_number) AS maximum_cardinality,
- CAST((ss.x).n AS sql_identifier) AS dtd_identifier
+ CAST((ss.x).n AS sql_identifier) AS dtd_identifier,
+ CAST(
+ CASE WHEN pg_has_role(proowner, 'USAGE')
+ THEN pg_get_function_arg_default(p_oid, (ss.x).n)
+ ELSE NULL END
+ AS character_data) AS parameter_default
FROM pg_type t, pg_namespace nt,
- (SELECT n.nspname AS n_nspname, p.proname, p.oid AS p_oid,
+ (SELECT n.nspname AS n_nspname, p.proname, p.oid AS p_oid, p.proowner,
p.proargnames, p.proargmodes,
_pg_expandarray(coalesce(p.proallargtypes, p.proargtypes::oid[])) AS x
FROM pg_namespace n, pg_proc p
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 266cec5..b9ebb78 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2248,6 +2248,76 @@ static char *generate_function_name(Oid funcid, int nargs, List *argnames,
return argsprinted;
}
+Datum
+pg_get_function_arg_default(PG_FUNCTION_ARGS)
+{
+ Oid funcid = PG_GETARG_OID(0);
+ int32 argn = PG_GETARG_INT32(1);
+ HeapTuple proctup;
+ Form_pg_proc proc;
+ int numargs;
+ Oid *argtypes;
+ char **argnames;
+ char *argmodes;
+ int i;
+ List *argdefaults;
+ Node *node;
+ char *str;
+ int inputargn;
+ Datum proargdefaults;
+ bool isnull;
+ int nth;
+
+ proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
+ if (!HeapTupleIsValid(proctup))
+ elog(ERROR, "cache lookup failed for function %u", funcid);
+
+ numargs = get_func_arg_info(proctup, &argtypes, &argnames, &argmodes);
+ if (argn > numargs)
+ {
+ ReleaseSysCache(proctup);
+ PG_RETURN_NULL();
+ }
+
+ inputargn = 0;
+
+ for (i = 0; i < argn; i++)
+ {
+ if (!argmodes || argmodes[i] == PROARGMODE_IN || argmodes[i] == PROARGMODE_INOUT || argmodes[i] == PROARGMODE_VARIADIC)
+ inputargn++;
+ }
+
+ proargdefaults = SysCacheGetAttr(PROCOID, proctup,
+ Anum_pg_proc_proargdefaults,
+ &isnull);
+
+ if (isnull)
+ {
+ ReleaseSysCache(proctup);
+ PG_RETURN_NULL();
+ }
+
+ str = TextDatumGetCString(proargdefaults);
+ argdefaults = (List *) stringToNode(str);
+ Assert(IsA(argdefaults, List));
+ pfree(str);
+
+ proc = (Form_pg_proc) GETSTRUCT(proctup);
+
+ nth = inputargn - 1 - (proc->pronargs - proc->pronargdefaults);
+ if (nth < 0 || nth >= list_length(argdefaults))
+ {
+ ReleaseSysCache(proctup);
+ PG_RETURN_NULL();
+ }
+ node = list_nth(argdefaults, nth);
+ str = deparse_expression_pretty(node, NIL, false, false, 0, 0);
+
+ ReleaseSysCache(proctup);
+
+ PG_RETURN_TEXT_P(string_to_text(str));
+}
+
/*
* deparse_expression - General utility for deparsing expressions
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 1e235c6..dc38532 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201212081
+#define CATALOG_VERSION_NO 201212261
#endif
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 010605d..64fbe7e 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -1964,6 +1964,8 @@ DATA(insert OID = 2232 ( pg_get_function_identity_arguments PGNSP PGUID 12 1
DESCR("identity argument list of a function");
DATA(insert OID = 2165 ( pg_get_function_result PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 25 "26" _null_ _null_ _null_ _null_ pg_get_function_result _null_ _null_ _null_ ));
DESCR("result type of a function");
+DATA(insert OID = 3839 ( pg_get_function_arg_default PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 25 "26 23" _null_ _null_ _null_ _null_ pg_get_function_arg_default _null_ _null_ _null_ ));
+DESCR("function argument default");
DATA(insert OID = 1686 ( pg_get_keywords PGNSP PGUID 12 10 400 0 0 f f f f t t s 0 0 2249 "" "{25,18,25}" "{o,o,o}" "{word,catcode,catdesc}" _null_ pg_get_keywords _null_ _null_ _null_ ));
DESCR("list of SQL keywords");
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 61d6aef..ed27116 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -652,6 +652,7 @@ extern Datum pg_get_functiondef(PG_FUNCTION_ARGS);
extern Datum pg_get_function_arguments(PG_FUNCTION_ARGS);
extern Datum pg_get_function_identity_arguments(PG_FUNCTION_ARGS);
extern Datum pg_get_function_result(PG_FUNCTION_ARGS);
+extern Datum pg_get_function_arg_default(PG_FUNCTION_ARGS);
extern char *deparse_expression(Node *expr, List *dpcontext,
bool forceprefix, bool showimplicit);
extern List *deparse_context_for(const char *aliasname, Oid relid);
diff --git a/src/test/regress/expected/create_function_3.out b/src/test/regress/expected/create_function_3.out
index e795232..101274d 100644
--- a/src/test/regress/expected/create_function_3.out
+++ b/src/test/regress/expected/create_function_3.out
@@ -425,9 +425,22 @@ SELECT proname, proisstrict FROM pg_proc
functext_f_4 | t
(4 rows)
+-- information_schema tests
+CREATE FUNCTION functest1(a int, b int default 1, c text default 'foo')
+ RETURNS int
+ LANGUAGE SQL
+ AS 'SELECT $1 + $2';
+SELECT ordinal_position, parameter_name, parameter_default FROM information_schema.parameters WHERE specific_schema = 'temp_func_test' AND specific_name LIKE 'functest1%' ORDER BY 1;
+ ordinal_position | parameter_name | parameter_default
+------------------+----------------+-------------------
+ 1 | a |
+ 2 | b | 1
+ 3 | c | 'foo'::text
+(3 rows)
+
-- Cleanups
DROP SCHEMA temp_func_test CASCADE;
-NOTICE: drop cascades to 16 other objects
+NOTICE: drop cascades to 17 other objects
DETAIL: drop cascades to function functest_a_1(text,date)
drop cascades to function functest_a_2(text[])
drop cascades to function functest_a_3()
@@ -444,5 +457,6 @@ drop cascades to function functext_f_1(integer)
drop cascades to function functext_f_2(integer)
drop cascades to function functext_f_3(integer)
drop cascades to function functext_f_4(integer)
+drop cascades to function functest1(integer,integer,text)
DROP USER regtest_unpriv_user;
RESET search_path;
diff --git a/src/test/regress/sql/create_function_3.sql b/src/test/regress/sql/create_function_3.sql
index e2dd9a3..c02faad 100644
--- a/src/test/regress/sql/create_function_3.sql
+++ b/src/test/regress/sql/create_function_3.sql
@@ -138,6 +138,17 @@ CREATE FUNCTION functext_F_4(int) RETURNS bool LANGUAGE 'sql'
'functext_F_3'::regproc,
'functext_F_4'::regproc) ORDER BY proname;
+
+-- information_schema tests
+
+CREATE FUNCTION functest1(a int, b int default 1, c text default 'foo')
+ RETURNS int
+ LANGUAGE SQL
+ AS 'SELECT $1 + $2';
+
+SELECT ordinal_position, parameter_name, parameter_default FROM information_schema.parameters WHERE specific_schema = 'temp_func_test' AND specific_name LIKE 'functest1%' ORDER BY 1;
+
+
-- Cleanups
DROP SCHEMA temp_func_test CASCADE;
DROP USER regtest_unpriv_user;
--
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