It seems that SPI_prepare() doesn't work well in some cases.

Pawel Pierscionek [pawel@astercity.net] reported about the
following case 1([SQL] drop table in pgsql).
Michael Contzen [mcontzen@dohle.com] reported about the
following case 2(PL/PGSQL bug using aggregates).
You can find it from pgsql-hackers archive.

1. PL/pgSQL can't execute UTILITY commands.
   SPI_prepare() doesn't copy(save) the utilityStmt member of
   Query type nodes,because copyObject() is not implemented
   for nodes of (Create/Destroy etc)Stmt type.

2. Aggregates in PL/pgSQL cause wrong results.

...
   It's a list including Aggreg type nodes which exist in
   TargetList(i.e Aggreg type nodes are common to aggs
   member list and TargetList).
   AFAIC the common pointer is not copied to the same
   pointer by copyObject() function.
   In my patch I reconstruct aggs member node from
   new(copied) Agg type node.
   Is it proper to use set_agg_tlist_references() function to
   reconstruct aggs member node for Agg type nodes ?

Thanks.

Hiroshi Inoue
Inoue@tpf.co.jp

src/backend/nodes/copyfuncs.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.52 1999/01/21 16:38:36 vadim Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.53 1999/01/21 22:55:41 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -506,7 +506,7 @@ _copyAgg(Agg *from)
 
 	CopyPlanFields((Plan *) from, (Plan *) newnode);
 
-	Node_Copy(from, newnode, aggs);
+	newnode->aggs = set_agg_tlist_references(newnode);
 	Node_Copy(from, newnode, aggstate);
 
 	return newnode;