From e034e517a70265a2e7f9552d2a9fd33102d21896 Mon Sep 17 00:00:00 2001
From: Neil Conway <neilc@samurai.com>
Date: Thu, 16 Oct 2008 19:25:55 +0000
Subject: [PATCH] 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 on was allocated in the per-query context, but we reallocated every
time the Agg node was rescanned. Since this information doesn't change over a
rescan, just construct the list of columns once during ExecInitAgg().
---
src/backend/executor/nodeAgg.c | 67 ++++++++++++++++++++--------------
1 file changed, 39 insertions(+), 28 deletions(-)
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index 80263d174c2..1af10dfefc3 100644
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -61,7 +61,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.161 2008/09/08 00:22:55 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.162 2008/10/16 19:25:55 neilc Exp $
*
*-------------------------------------------------------------------------
*/
@@ -665,9 +665,6 @@ build_hash_table(AggState *aggstate)
Agg *node = (Agg *) aggstate->ss.ps.plan;
MemoryContext tmpmem = aggstate->tmpcontext->ecxt_per_tuple_memory;
Size entrysize;
- Bitmapset *colnos;
- List *collist;
- int i;
Assert(node->aggstrategy == AGG_HASHED);
Assert(node->numGroups > 0);
@@ -683,30 +680,40 @@ build_hash_table(AggState *aggstate)
entrysize,
aggstate->aggcontext,
tmpmem);
+}
- /*
- * Create a list of the tuple columns that actually need to be stored in
- * hashtable entries. The incoming tuples from the child plan node will
- * contain grouping columns, other columns referenced in our targetlist
- * and qual, columns used to compute the aggregate functions, and perhaps
- * just junk columns we don't use at all. Only columns of the first two
- * types need to be stored in the hashtable, and getting rid of the others
- * can make the table entries significantly smaller. To avoid messing up
- * Var numbering, we keep the same tuple descriptor for hashtable entries
- * as the incoming tuples have, but set unwanted columns to NULL in the
- * tuples that go into the table.
- *
- * To eliminate duplicates, we build a bitmapset of the needed columns,
- * then convert it to an integer list (cheaper to scan at runtime). The
- * list is in decreasing order so that the first entry is the largest;
- * lookup_hash_entry depends on this to use slot_getsomeattrs correctly.
- *
- * Note: at present, searching the tlist/qual is not really necessary
- * since the parser should disallow any unaggregated references to
- * ungrouped columns. However, the search will be needed when we add
- * support for SQL99 semantics that allow use of "functionally dependent"
- * columns that haven't been explicitly grouped by.
- */
+/*
+ * Create a list of the tuple columns that actually need to be stored in
+ * hashtable entries. The incoming tuples from the child plan node will
+ * contain grouping columns, other columns referenced in our targetlist and
+ * qual, columns used to compute the aggregate functions, and perhaps just
+ * junk columns we don't use at all. Only columns of the first two types
+ * need to be stored in the hashtable, and getting rid of the others can
+ * make the table entries significantly smaller. To avoid messing up Var
+ * numbering, we keep the same tuple descriptor for hashtable entries as the
+ * incoming tuples have, but set unwanted columns to NULL in the tuples that
+ * go into the table.
+ *
+ * To eliminate duplicates, we build a bitmapset of the needed columns, then
+ * convert it to an integer list (cheaper to scan at runtime). The list is
+ * in decreasing order so that the first entry is the largest;
+ * lookup_hash_entry depends on this to use slot_getsomeattrs correctly.
+ * Note that the list is preserved over ExecReScanAgg, so we allocate it in
+ * the per-query context (unlike the hash table itself).
+ *
+ * Note: at present, searching the tlist/qual is not really necessary since
+ * the parser should disallow any unaggregated references to ungrouped
+ * columns. However, the search will be needed when we add support for
+ * SQL99 semantics that allow use of "functionally dependent" columns that
+ * haven't been explicitly grouped by.
+ */
+static List *
+find_hash_columns(AggState *aggstate)
+{
+ Agg *node = (Agg *) aggstate->ss.ps.plan;
+ Bitmapset *colnos;
+ List *collist;
+ int i;
/* Find Vars that will be needed in tlist and qual */
colnos = find_unaggregated_cols(aggstate);
@@ -717,7 +724,9 @@ build_hash_table(AggState *aggstate)
collist = NIL;
while ((i = bms_first_member(colnos)) >= 0)
collist = lcons_int(i, collist);
- aggstate->hash_needed = collist;
+ bms_free(colnos);
+
+ return collist;
}
/*
@@ -1325,6 +1334,8 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
{
build_hash_table(aggstate);
aggstate->table_filled = false;
+ /* Compute the columns we actually need to hash on */
+ aggstate->hash_needed = find_hash_columns(aggstate);
}
else
{
--
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