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Fix qual_is_pushdown_safe to not try to push down quals involving a whole-row

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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).
This commit is contained in:
Tom Lane 2006-02-13 16:22:23 +00:00
parent 562f63b0a7
commit 4299a92d3c
1 changed files with 17 additions and 7 deletions
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24
src/backend/optimizer/path/allpaths.c
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@ -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;