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Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans

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had stopped working for tables buried inside views or sub-selects.  This is
because I had gotten rid of the simplify_jointree() preprocessing step, and
optimize_minmax_aggregates() wasn't smart enough to deal with a non-canonical
FromExpr.  Per gripe from Bill Howe.
This commit is contained in:
Tom Lane 2007-02-06 06:50:33 +00:00
parent 5338847fcd
commit a95abdf856
1 changed files with 13 additions and 7 deletions
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20
src/backend/optimizer/plan/planagg.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.22 2006/10/04 00:29:54 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.22.2.1 2007/02/06 06:50:33 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -69,6 +69,7 @@ Plan *
optimize_minmax_aggregates(PlannerInfo *root, List *tlist, Path *best_path)
{
Query *parse = root->parse;
FromExpr *jtnode;
RangeTblRef *rtr;
RangeTblEntry *rte;
RelOptInfo *rel;
@ -101,14 +102,19 @@ optimize_minmax_aggregates(PlannerInfo *root, List *tlist, Path *best_path)
* We also restrict the query to reference exactly one table, since join
* conditions can't be handled reasonably. (We could perhaps handle a
* query containing cartesian-product joins, but it hardly seems worth the
* trouble.)
* trouble.) However, the single real table could be buried in several
* levels of FromExpr.
*/
Assert(parse->jointree != NULL && IsA(parse->jointree, FromExpr));
if (list_length(parse->jointree->fromlist) != 1)
return NULL;
rtr = (RangeTblRef *) linitial(parse->jointree->fromlist);
if (!IsA(rtr, RangeTblRef))
jtnode = parse->jointree;
while (IsA(jtnode, FromExpr))
{
if (list_length(jtnode->fromlist) != 1)
return NULL;
jtnode = linitial(jtnode->fromlist);
}
if (!IsA(jtnode, RangeTblRef))
return NULL;
rtr = (RangeTblRef *) jtnode;
rte = rt_fetch(rtr->rtindex, parse->rtable);
if (rte->rtekind != RTE_RELATION || rte->inh)
return NULL;