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Commit7ace43e

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committed
Fix oversight in MIN/MAX optimization: must not return NULL entries
from index, since the aggregates ignore NULLs.
1 parent2e7a688 commit7ace43e

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3 files changed

+28
-14
lines changed

3 files changed

+28
-14
lines changed

‎src/backend/optimizer/plan/createplan.c‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
*
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.178 2005/04/06 16:34:05 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.179 2005/04/12 05:11:28 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -73,7 +73,6 @@ static void fix_indxqual_sublist(List *indexqual, IndexOptInfo *index,
7373
staticNode*fix_indxqual_operand(Node*node,IndexOptInfo*index,
7474
Oid*opclass);
7575
staticList*get_switched_clauses(List*clauses,Relidsouterrelids);
76-
staticList*order_qual_clauses(Query*root,List*clauses);
7776
staticvoidcopy_path_costsize(Plan*dest,Path*src);
7877
staticvoidcopy_plan_costsize(Plan*dest,Plan*src);
7978
staticSeqScan*make_seqscan(List*qptlist,List*qpqual,Indexscanrelid);
@@ -1417,7 +1416,7 @@ get_switched_clauses(List *clauses, Relids outerrelids)
14171416
* For now, we just move any quals that contain SubPlan references (but not
14181417
* InitPlan references) to the end of the list.
14191418
*/
1420-
staticList*
1419+
List*
14211420
order_qual_clauses(Query*root,List*clauses)
14221421
{
14231422
List*nosubplans;

‎src/backend/optimizer/plan/planagg.c‎

Lines changed: 24 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.2 2005/04/1204:26:24 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.3 2005/04/1205:11:28 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -185,6 +185,8 @@ optimize_minmax_aggregates(Query *root, List *tlist, Path *best_path)
185185
{
186186
Assert(((ResultPath*)best_path)->subpath!=NULL);
187187
constant_quals= ((ResultPath*)best_path)->constantqual;
188+
/* no need to do this more than once: */
189+
constant_quals=order_qual_clauses(root,constant_quals);
188190
}
189191
else
190192
constant_quals=NIL;
@@ -438,10 +440,10 @@ static void
438440
make_agg_subplan(Query*root,MinMaxAggInfo*info,List*constant_quals)
439441
{
440442
Query*subquery;
441-
Path*path;
442443
Plan*plan;
443444
TargetEntry*tle;
444445
SortClause*sortcl;
446+
NullTest*ntest;
445447

446448
/*
447449
* Generate a suitably modified Query node. Much of the work here is
@@ -482,18 +484,30 @@ make_agg_subplan(Query *root, MinMaxAggInfo *info, List *constant_quals)
482484
* Generate the plan for the subquery. We already have a Path for
483485
* the basic indexscan, but we have to convert it to a Plan and
484486
* attach a LIMIT node above it. We might need a gating Result, too,
485-
* which is most easily added at the Path stage.
487+
* to handle any non-variable qual clauses.
488+
*
489+
* Also we must add a "WHERE foo IS NOT NULL" restriction to the
490+
* indexscan, to be sure we don't return a NULL, which'd be contrary
491+
* to the standard behavior of MIN/MAX. XXX ideally this should be
492+
* done earlier, so that the selectivity of the restriction could be
493+
* included in our cost estimates. But that looks painful, and in
494+
* most cases the fraction of NULLs isn't high enough to change the
495+
* decision.
486496
*/
487-
path=(Path*)info->path;
497+
plan=create_plan(subquery, (Path*)info->path);
488498

489-
if (constant_quals)
490-
path= (Path*)create_result_path(NULL,
491-
path,
492-
copyObject(constant_quals));
499+
plan->targetlist=copyObject(subquery->targetList);
493500

494-
plan=create_plan(subquery,path);
501+
ntest=makeNode(NullTest);
502+
ntest->nulltesttype=IS_NOT_NULL;
503+
ntest->arg=copyObject(info->target);
495504

496-
plan->targetlist=copyObject(subquery->targetList);
505+
plan->qual=lappend(plan->qual,ntest);
506+
507+
if (constant_quals)
508+
plan= (Plan*)make_result(copyObject(plan->targetlist),
509+
copyObject(constant_quals),
510+
plan);
497511

498512
plan= (Plan*)make_limit(plan,
499513
subquery->limitOffset,

‎src/include/optimizer/planmain.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.81 2005/04/11 23:06:56 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.82 2005/04/12 05:11:28 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -40,6 +40,7 @@ extern Sort *make_sort_from_sortclauses(Query *root, List *sortcls,
4040
Plan*lefttree);
4141
externSort*make_sort_from_groupcols(Query*root,List*groupcls,
4242
AttrNumber*grpColIdx,Plan*lefttree);
43+
externList*order_qual_clauses(Query*root,List*clauses);
4344
externAgg*make_agg(Query*root,List*tlist,List*qual,
4445
AggStrategyaggstrategy,
4546
intnumGroupCols,AttrNumber*grpColIdx,

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