Fix an oversight in convert_EXISTS_sublink_to_join: we can't convert an

EXISTS that contains a WITH clause.  This would usually lead to a
"could not find CTE" error later in planning, because the WITH wouldn't
get processed at all.  Noted while playing with an example from Ken Marshall.

diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 887f360c0ee5cbad1d6eefe566b9c75301a15d01..2e99cc6b4ba8ce8097543026bdfffc962a2ed357 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
- *   $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.157 2010/01/02 16:57:47 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.158 2010/01/18 18:17:45 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1114,6 +1114,17 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
 
    Assert(sublink->subLinkType == EXISTS_SUBLINK);
 
+   /*
+    * Can't flatten if it contains WITH.  (We could arrange to pull up the
+    * WITH into the parent query's cteList, but that risks changing the
+    * semantics, since a WITH ought to be executed once per associated query
+    * call.)  Note that convert_ANY_sublink_to_join doesn't have to reject
+    * this case, since it just produces a subquery RTE that doesn't have to
+    * get flattened into the parent query.
+    */
+   if (subselect->cteList)
+       return NULL;
+
    /*
     * Copy the subquery so we can modify it safely (see comments in
     * make_subplan).