Back-patch fix to copy sub-Query nodes before planning them. This

fixes problems with subselects appearing in contexts like COALESCE or
BETWEEN, where parser will make multiple links to same subexpression.

diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 373b05d42fe79c4038871585d38ed28a911fa617..29e4a69c2d12408b4bfa6adcb1165c7009ab38ca 100644 (file)
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.36 2000/04/14 00:19:16 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.36.2.1 2000/09/23 21:00:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -136,13 +136,24 @@ make_subplan(SubLink *slink)
 
        PlannerQueryLevel++;            /* we become child */
 
-       /* Check to see if this node was already processed; if so we have
-        * trouble.  Someday should change tree representation so that we can
-        * cope with multiple links to the same subquery, but for now...
+       /*
+        * Check to see if this node was already processed; if so we have
+        * trouble.  We check to see if the linked-to Query appears to have
+        * been planned already, too.
         */
        if (subquery == NULL)
+               elog(ERROR, "make_subplan: invalid expression structure (SubLink already processed?)");
+       if (subquery->base_rel_list != NIL)
                elog(ERROR, "make_subplan: invalid expression structure (subquery already processed?)");
 
+       /*
+        * Copy the source Query node.  This is a quick and dirty kluge to resolve
+        * the fact that the parser can generate trees with multiple links to the
+        * same sub-Query node, but the planner wants to scribble on the Query.
+        * Try to clean this up when we do querytree redesign...
+        */
+       subquery = (Query *) copyObject(subquery);
+
        /*
         * For an EXISTS subplan, tell lower-level planner to expect that only
         * the first tuple will be retrieved.  For ALL and ANY subplans, we