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Fix a gradual memory leak in ExecReScanAgg(). Because the aggregation

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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.
This commit is contained in:
Neil Conway 2007-08-08 18:06:55 +00:00
parent b58230005b
commit 7824c695ac
1 changed files with 9 additions and 3 deletions
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12
src/backend/executor/nodeAgg.c
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@ -45,7 +45,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.116.2.3 2005/01/27 23:43:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.116.2.4 2007/08/08 18:06:55 neilc Exp $
*
*-------------------------------------------------------------------------
*/
@ -1509,8 +1509,14 @@ 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)
{