From c556b29a1199babc672b81065fe74fb50657c451 Mon Sep 17 00:00:00 2001
From: Neil Conway <neilc@samurai.com>
Date: Wed, 8 Aug 2007 18:07:05 +0000
Subject: [PATCH] Fix a gradual memory leak in ExecReScanAgg(). Because the
aggregation hash table is allocated in a child context of the agg node's
memory context, MemoryContextReset() will reset but *not* delete the child
context. Since ExecReScanAgg() proceeds to build a new hash table from
scratch (in a new sub-context), this results in leaking the header for the
previous memory context. Therefore, use MemoryContextResetAndDeleteChildren()
instead.
Credit: My colleague Sailesh Krishnamurthy at Truviso for isolating
the cause of the leak.
---
src/backend/executor/nodeAgg.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index d9e26d1d196..644268b6350 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 1.152 2007/04/02 03:49:38 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.153 2007/08/08 18:07:05 neilc Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1646,8 +1646,14 @@ ExecReScanAgg(AggState *node, ExprContext *exprCtxt)
MemSet(econtext->ecxt_aggvalues, 0, sizeof(Datum) * node->numaggs);
MemSet(econtext->ecxt_aggnulls, 0, sizeof(bool) * node->numaggs);
- /* Release all temp storage */
- MemoryContextReset(node->aggcontext);
+ /*
+ * Release all temp storage. Note that with AGG_HASHED, the hash table
+ * is allocated in a sub-context of the aggcontext. We're going to
+ * rebuild the hash table from scratch, so we need to use
+ * MemoryContextResetAndDeleteChildren() to avoid leaking the old hash
+ * table's memory context header.
+ */
+ MemoryContextResetAndDeleteChildren(node->aggcontext);
if (((Agg *) node->ss.ps.plan)->aggstrategy == AGG_HASHED)
{
--
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