Avoid pulling up sublinks from a subselect's targetlist. Works around

problems that occur if sublink is referenced via a join alias variable.
Perhaps this can be improved later, but a simple and safe fix is needed
for 7.3.1.

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 0e5afccae3adede688a1ca71e17fab10c940a69d..ebb9f3d2092f43c8db0b062ac28961c3b51293c8 100644 (file)
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.132 2002/11/29 21:39:11 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.133 2002/12/05 21:46:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -357,10 +357,14 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
             * nothing will happen after the first time.  We do have to be
             * careful to copy everything we pull up, however, or risk
             * having chunks of structure multiply linked.
+            *
+            * Note: 'false' is correct here even if we are within an outer
+            * join in the upper query; the lower query starts with a clean
+            * slate for outer-join semantics.
             */
            subquery->jointree = (FromExpr *)
                pull_up_subqueries(subquery, (Node *) subquery->jointree,
-                                  below_outer_join);
+                                  false);
 
            /*
             * Now make a modifiable copy of the subquery that we can run
@@ -542,6 +546,20 @@ is_simple_subquery(Query *subquery)
    if (expression_returns_set((Node *) subquery->targetList))
        return false;
 
+   /*
+    * Don't pull up a subquery that has any sublinks in its targetlist,
+    * either.  As of PG 7.3 this creates problems because the pulled-up
+    * expressions may go into join alias lists, and the sublinks would
+    * not get fixed because we do flatten_join_alias_vars() too late.
+    * Eventually we should do a complete flatten_join_alias_vars as the
+    * first step of preprocess_expression, and then we could probably
+    * support this.  (BUT: it might be a bad idea anyway, due to possibly
+    * causing multiple evaluations of an expensive sublink.)
+    */
+   if (subquery->hasSubLinks &&
+       contain_subplans((Node *) subquery->targetList))
+       return false;
+
    /*
     * Hack: don't try to pull up a subquery with an empty jointree.
     * query_planner() will correctly generate a Result plan for a