From 4299a92d3cdbced57de9606df87cc8ec3163f2f0 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 13 Feb 2006 16:22:23 +0000
Subject: [PATCH] Fix qual_is_pushdown_safe to not try to push down quals
involving a whole-row Var referencing the subselect output. While this case
could possibly be made to work, it seems not worth expending effort on. Per
report from Magnus Naeslund(f).
---
src/backend/optimizer/path/allpaths.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index d2100905406..c2fd30d5145 100644
--- 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 1.142 2006/02/04 23:03:20 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.143 2006/02/13 16:22:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -816,11 +816,14 @@ compare_tlist_datatypes(List *tlist, List *colTypes,
* it will work correctly: sublinks will already have been transformed into
* subplans in the qual, but not in the subquery).
*
- * 2. The qual must not refer to any subquery output columns that were
+ * 2. The qual must not refer to the whole-row output of the subquery
+ * (since there is no easy way to name that within the subquery itself).
+ *
+ * 3. The qual must not refer to any subquery output columns that were
* found to have inconsistent types across a set operation tree by
* subquery_is_pushdown_safe().
*
- * 3. If the subquery uses DISTINCT ON, we must not push down any quals that
+ * 4. If the subquery uses DISTINCT ON, we must not push down any quals that
* refer to non-DISTINCT output columns, because that could change the set
* of rows returned. This condition is vacuous for DISTINCT, because then
* there are no non-DISTINCT output columns, but unfortunately it's fairly
@@ -828,7 +831,7 @@ compare_tlist_datatypes(List *tlist, List *colTypes,
* parsetree representation. It's cheaper to just make sure all the Vars
* in the qual refer to DISTINCT columns.
*
- * 4. We must not push down any quals that refer to subselect outputs that
+ * 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.
*/
@@ -857,6 +860,13 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
Assert(var->varno == rti);
+ /* Check point 2 */
+ if (var->varattno == 0)
+ {
+ safe = false;
+ break;
+ }
+
/*
* We use a bitmapset to avoid testing the same attno more than once.
* (NB: this only works because subquery outputs can't have negative
@@ -866,7 +876,7 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
continue;
tested = bms_add_member(tested, var->varattno);
- /* Check point 2 */
+ /* Check point 3 */
if (differentTypes[var->varattno])
{
safe = false;
@@ -878,7 +888,7 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
Assert(tle != NULL);
Assert(!tle->resjunk);
- /* If subquery uses DISTINCT or DISTINCT ON, check point 3 */
+ /* If subquery uses DISTINCT or DISTINCT ON, check point 4 */
if (subquery->distinctClause != NIL &&
!targetIsInSortList(tle, subquery->distinctClause))
{
@@ -887,7 +897,7 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
break;
}
- /* Refuse functions returning sets (point 4) */
+ /* Refuse functions returning sets (point 5) */
if (expression_returns_set((Node *) tle->expr))
{
safe = false;
--
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