From 27ae96c2b63c6ba68a2b8776cdd478dc779b641d Mon Sep 17 00:00:00 2001
From: Joe Conway <mail@joeconway.com>
Date: Tue, 24 Feb 2004 06:07:34 +0000
Subject: [PATCH] When returning type "record", replace use of
 pgresultGetTupleDesc with ReturnSetInfo->expectedDesc. This allows custom
 datatypes (e.g. from tsearch2) to be returned at runtime. Previous behavior
 depended on the type oid to match between the remote and local database,
 which obviously doesn't work well for custom types. Per report from Mark
 Gibson.

---
 contrib/dblink/dblink.c | 82 +++++++++++------------------------------
 1 file changed, 22 insertions(+), 60 deletions(-)

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index ad5365595c7..3fea501b60c 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -82,7 +82,6 @@ static char *quote_ident_cstr(char *rawstr);
 static int16 get_attnum_pk_pos(int16 *pkattnums, int16 pknumatts, int16 key);
 static HeapTuple get_tuple_of_interest(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals);
 static Oid	get_relid_from_relname(text *relname_text);
-static TupleDesc pgresultGetTupleDesc(PGresult *res);
 static char *generate_relation_name(Oid relid);
 
 /* Global */
@@ -395,6 +394,7 @@ dblink_fetch(PG_FUNCTION_ARGS)
 		StringInfo	str = makeStringInfo();
 		char	   *curname = NULL;
 		int			howmany = 0;
+		ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 
 		if (PG_NARGS() == 3)
 		{
@@ -457,7 +457,16 @@ dblink_fetch(PG_FUNCTION_ARGS)
 		if (functyptype == 'c')
 			tupdesc = TypeGetTupleDesc(functypeid, NIL);
 		else if (functyptype == 'p' && functypeid == RECORDOID)
-			tupdesc = pgresultGetTupleDesc(res);
+		{
+			if (!rsinfo || !IsA(rsinfo, ReturnSetInfo))
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("function returning record called in context "
+								"that cannot accept type record")));
+
+			/* get the requested return tuple description */
+			tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
+		}
 		else
 			/* shouldn't happen */
 			elog(ERROR, "return type must be a row type");
@@ -550,6 +559,7 @@ dblink_record(PG_FUNCTION_ARGS)
 		char	   *sql = NULL;
 		char	   *conname = NULL;
 		remoteConn *rcon = NULL;
+		ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 
 		/* create a function context for cross-call persistence */
 		funcctx = SRF_FIRSTCALL_INIT();
@@ -620,7 +630,16 @@ dblink_record(PG_FUNCTION_ARGS)
 			if (functyptype == 'c')
 				tupdesc = TypeGetTupleDesc(functypeid, NIL);
 			else if (functyptype == 'p' && functypeid == RECORDOID)
-				tupdesc = pgresultGetTupleDesc(res);
+			{
+				if (!rsinfo || !IsA(rsinfo, ReturnSetInfo))
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+							 errmsg("function returning record called in context "
+									"that cannot accept type record")));
+
+				/* get the requested return tuple description */
+				tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
+			}
 			else
 				/* shouldn't happen */
 				elog(ERROR, "return type must be a row type");
@@ -1801,63 +1820,6 @@ get_relid_from_relname(text *relname_text)
 	return relid;
 }
 
-static TupleDesc
-pgresultGetTupleDesc(PGresult *res)
-{
-	int			natts;
-	AttrNumber	attnum;
-	TupleDesc	desc;
-	char	   *attname;
-	int32		atttypmod;
-	int			attdim;
-	bool		attisset;
-	Oid			atttypid;
-	int			i;
-
-	/*
-	 * allocate a new tuple descriptor
-	 */
-	natts = PQnfields(res);
-	if (natts < 1)
-		/* shouldn't happen */
-		elog(ERROR, "cannot create a description for empty results");
-
-	desc = CreateTemplateTupleDesc(natts, false);
-
-	attnum = 0;
-
-	for (i = 0; i < natts; i++)
-	{
-		/*
-		 * for each field, get the name and type information from the
-		 * query result and have TupleDescInitEntry fill in the attribute
-		 * information we need.
-		 */
-		attnum++;
-
-		attname = PQfname(res, i);
-		atttypid = PQftype(res, i);
-		atttypmod = PQfmod(res, i);
-
-		if (PQfsize(res, i) != get_typlen(atttypid))
-			ereport(ERROR,
-					(errcode(ERRCODE_MOST_SPECIFIC_TYPE_MISMATCH),
-					 errmsg("field size mismatch"),
-				errdetail("Size of remote field \"%s\" does not match " \
-						  "size of local type \"%s\".", attname,
-						  format_type_with_typemod(atttypid,
-												   atttypmod))));
-
-		attdim = 0;
-		attisset = false;
-
-		TupleDescInitEntry(desc, attnum, attname, atttypid,
-						   atttypmod, attdim, attisset);
-	}
-
-	return desc;
-}
-
 /*
  * generate_relation_name - copied from ruleutils.c
  *		Compute the name to display for a relation specified by OID