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Commite034e51

Browse files
author
Neil Conway
committed
Fix a small memory leak in ExecReScanAgg() in the hashed aggregation case.
In the previous coding, the list of columns that needed to be hashed onwas allocated in the per-query context, but we reallocated every timethe Agg node was rescanned. Since this information doesn't change overa rescan, just construct the list of columns once during ExecInitAgg().
1 parent0e3d5ad commite034e51

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1 file changed

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-28
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1 file changed

+39
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‎src/backend/executor/nodeAgg.c‎

Lines changed: 39 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -61,7 +61,7 @@
6161
* Portions Copyright (c) 1994, Regents of the University of California
6262
*
6363
* IDENTIFICATION
64-
* $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.161 2008/09/08 00:22:55tgl Exp $
64+
* $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.162 2008/10/16 19:25:55neilc Exp $
6565
*
6666
*-------------------------------------------------------------------------
6767
*/
@@ -665,9 +665,6 @@ build_hash_table(AggState *aggstate)
665665
Agg*node= (Agg*)aggstate->ss.ps.plan;
666666
MemoryContexttmpmem=aggstate->tmpcontext->ecxt_per_tuple_memory;
667667
Sizeentrysize;
668-
Bitmapset*colnos;
669-
List*collist;
670-
inti;
671668

672669
Assert(node->aggstrategy==AGG_HASHED);
673670
Assert(node->numGroups>0);
@@ -683,30 +680,40 @@ build_hash_table(AggState *aggstate)
683680
entrysize,
684681
aggstate->aggcontext,
685682
tmpmem);
683+
}
686684

687-
/*
688-
* Create a list of the tuple columns that actually need to be stored in
689-
* hashtable entries. The incoming tuples from the child plan node will
690-
* contain grouping columns, other columns referenced in our targetlist
691-
* and qual, columns used to compute the aggregate functions, and perhaps
692-
* just junk columns we don't use at all. Only columns of the first two
693-
* types need to be stored in the hashtable, and getting rid of the others
694-
* can make the table entries significantly smaller. To avoid messing up
695-
* Var numbering, we keep the same tuple descriptor for hashtable entries
696-
* as the incoming tuples have, but set unwanted columns to NULL in the
697-
* tuples that go into the table.
698-
*
699-
* To eliminate duplicates, we build a bitmapset of the needed columns,
700-
* then convert it to an integer list (cheaper to scan at runtime). The
701-
* list is in decreasing order so that the first entry is the largest;
702-
* lookup_hash_entry depends on this to use slot_getsomeattrs correctly.
703-
*
704-
* Note: at present, searching the tlist/qual is not really necessary
705-
* since the parser should disallow any unaggregated references to
706-
* ungrouped columns. However, the search will be needed when we add
707-
* support for SQL99 semantics that allow use of "functionally dependent"
708-
* columns that haven't been explicitly grouped by.
709-
*/
685+
/*
686+
* Create a list of the tuple columns that actually need to be stored in
687+
* hashtable entries. The incoming tuples from the child plan node will
688+
* contain grouping columns, other columns referenced in our targetlist and
689+
* qual, columns used to compute the aggregate functions, and perhaps just
690+
* junk columns we don't use at all. Only columns of the first two types
691+
* need to be stored in the hashtable, and getting rid of the others can
692+
* make the table entries significantly smaller. To avoid messing up Var
693+
* numbering, we keep the same tuple descriptor for hashtable entries as the
694+
* incoming tuples have, but set unwanted columns to NULL in the tuples that
695+
* go into the table.
696+
*
697+
* To eliminate duplicates, we build a bitmapset of the needed columns, then
698+
* convert it to an integer list (cheaper to scan at runtime). The list is
699+
* in decreasing order so that the first entry is the largest;
700+
* lookup_hash_entry depends on this to use slot_getsomeattrs correctly.
701+
* Note that the list is preserved over ExecReScanAgg, so we allocate it in
702+
* the per-query context (unlike the hash table itself).
703+
*
704+
* Note: at present, searching the tlist/qual is not really necessary since
705+
* the parser should disallow any unaggregated references to ungrouped
706+
* columns. However, the search will be needed when we add support for
707+
* SQL99 semantics that allow use of "functionally dependent" columns that
708+
* haven't been explicitly grouped by.
709+
*/
710+
staticList*
711+
find_hash_columns(AggState*aggstate)
712+
{
713+
Agg*node= (Agg*)aggstate->ss.ps.plan;
714+
Bitmapset*colnos;
715+
List*collist;
716+
inti;
710717

711718
/* Find Vars that will be needed in tlist and qual */
712719
colnos=find_unaggregated_cols(aggstate);
@@ -717,7 +724,9 @@ build_hash_table(AggState *aggstate)
717724
collist=NIL;
718725
while ((i=bms_first_member(colnos)) >=0)
719726
collist=lcons_int(i,collist);
720-
aggstate->hash_needed=collist;
727+
bms_free(colnos);
728+
729+
returncollist;
721730
}
722731

723732
/*
@@ -1325,6 +1334,8 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
13251334
{
13261335
build_hash_table(aggstate);
13271336
aggstate->table_filled= false;
1337+
/* Compute the columns we actually need to hash on */
1338+
aggstate->hash_needed=find_hash_columns(aggstate);
13281339
}
13291340
else
13301341
{

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