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Commit56e59ed

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Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans
had stopped working for tables buried inside views or sub-selects. This isbecause I had gotten rid of the simplify_jointree() preprocessing step, andoptimize_minmax_aggregates() wasn't smart enough to deal with a non-canonicalFromExpr. Per gripe from Bill Howe.
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‎src/backend/optimizer/plan/planagg.c‎

Lines changed: 13 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.25 2007/01/09 02:14:13 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.26 2007/02/06 06:50:26 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -70,6 +70,7 @@ Plan *
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optimize_minmax_aggregates(PlannerInfo*root,List*tlist,Path*best_path)
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{
7272
Query*parse=root->parse;
73+
FromExpr*jtnode;
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RangeTblRef*rtr;
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RangeTblEntry*rte;
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RelOptInfo*rel;
@@ -102,14 +103,19 @@ optimize_minmax_aggregates(PlannerInfo *root, List *tlist, Path *best_path)
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* We also restrict the query to reference exactly one table, since join
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* conditions can't be handled reasonably. (We could perhaps handle a
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* query containing cartesian-product joins, but it hardly seems worth the
105-
* trouble.)
106+
* trouble.) However, the single real table could be buried in several
107+
* levels of FromExpr.
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*/
107-
Assert(parse->jointree!=NULL&&IsA(parse->jointree,FromExpr));
108-
if (list_length(parse->jointree->fromlist)!=1)
109-
returnNULL;
110-
rtr= (RangeTblRef*)linitial(parse->jointree->fromlist);
111-
if (!IsA(rtr,RangeTblRef))
109+
jtnode=parse->jointree;
110+
while (IsA(jtnode,FromExpr))
111+
{
112+
if (list_length(jtnode->fromlist)!=1)
113+
returnNULL;
114+
jtnode=linitial(jtnode->fromlist);
115+
}
116+
if (!IsA(jtnode,RangeTblRef))
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returnNULL;
118+
rtr= (RangeTblRef*)jtnode;
113119
rte=rt_fetch(rtr->rtindex,parse->rtable);
114120
if (rte->rtekind!=RTE_RELATION||rte->inh)
115121
returnNULL;

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