Suppress subquery pullup/pushdown when a subquery contains volatile

functions in its targetlist, to avoid introducing multiple evaluations
of volatile functions that textually appear only once.  This is a
slightly tighter version of Jaime Casanova's recent patch.

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index fc618f72d1cc0878fafc8bff66a113c718de9391..794c14fbbabc2b05f1e468daa607e87a0d5734b2 100644 (file)
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.151 2006/08/10 02:36:28 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.152 2006/08/19 02:48:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -871,6 +871,10 @@ compare_tlist_datatypes(List *tlist, List *colTypes,
  * 5. We must not push down any quals that refer to subselect outputs that
  * return sets, else we'd introduce functions-returning-sets into the
  * subquery's WHERE/HAVING quals.
+ *
+ * 6. We must not push down any quals that refer to subselect outputs that
+ * contain volatile functions, for fear of introducing strange results due
+ * to multiple evaluation of a volatile function.
  */
 static bool
 qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
@@ -940,6 +944,13 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
                        safe = false;
                        break;
                }
+
+               /* Refuse volatile functions (point 6) */
+               if (contain_volatile_functions((Node *) tle->expr))
+               {
+                       safe = false;
+                       break;
+               }
        }
 
        list_free(vars);

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index ef92d9d3c9f33cb54e013f583dfa6d4849f90001..bea7c03a739e3ad01b89a1abb2b5a08d682ea945 100644 (file)
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.42 2006/08/12 20:05:55 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.43 2006/08/19 02:48:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -656,6 +656,15 @@ is_simple_subquery(Query *subquery)
        if (expression_returns_set((Node *) subquery->targetList))
                return false;
 
+       /*
+        * Don't pull up a subquery that has any volatile functions in its
+        * targetlist.  Otherwise we might introduce multiple evaluations of
+        * these functions, if they get copied to multiple places in the upper
+        * query, leading to surprising results.
+        */
+       if (contain_volatile_functions((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 jointree