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Commitbdc7f68

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Fix query-lifespan memory leakage in repeatedly executed hash joins.
ExecHashTableCreate allocated some memory that wasn't freed byExecHashTableDestroy, specifically the per-hash-key function information.That's not a huge amount of data, but if one runs a query that repeatsa hash join enough times, it builds up. Fix by arranging for the datain question to be kept in the hashtable's hashCxt instead of leaving it"loose" in the query-lifespan executor context. (This ensures that we'llalso clean up anything that the hash functions allocate in fn_mcxt.)Per report from Amit Khandekar. It's been like this forever, so back-patchto all supported branches.Discussion:https://postgr.es/m/CAJ3gD9cFofAWGvcxLOxDHC=B0hjtW8yGmUsF2hdGh97CM38=7g@mail.gmail.com
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‎src/backend/executor/nodeHash.c

Lines changed: 18 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -272,7 +272,8 @@ ExecHashTableCreate(Hash *node, List *hashOperators, bool keepNulls)
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* Initialize the hash table control block.
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*
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* The hashtable control block is just palloc'd from the executor's
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* per-query memory context.
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* per-query memory context. Everything else should be kept inside the
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* subsidiary hashCxt or batchCxt.
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*/
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hashtable= (HashJoinTable)palloc(sizeof(HashJoinTableData));
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hashtable->nbuckets=nbuckets;
@@ -309,6 +310,22 @@ ExecHashTableCreate(Hash *node, List *hashOperators, bool keepNulls)
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hashtable,nbatch,nbuckets);
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#endif
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/*
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* Create temporary memory contexts in which to keep the hashtable working
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* storage. See notes in executor/hashjoin.h.
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*/
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hashtable->hashCxt=AllocSetContextCreate(CurrentMemoryContext,
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"HashTableContext",
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ALLOCSET_DEFAULT_SIZES);
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hashtable->batchCxt=AllocSetContextCreate(hashtable->hashCxt,
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"HashBatchContext",
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ALLOCSET_DEFAULT_SIZES);
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/* Allocate data that will live for the life of the hashjoin */
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oldcxt=MemoryContextSwitchTo(hashtable->hashCxt);
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/*
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* Get info about the hash functions to be used for each hash key. Also
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* remember whether the join operators are strict.
@@ -335,22 +352,6 @@ ExecHashTableCreate(Hash *node, List *hashOperators, bool keepNulls)
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i++;
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}
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/*
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* Create temporary memory contexts in which to keep the hashtable working
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* storage. See notes in executor/hashjoin.h.
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*/
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hashtable->hashCxt=AllocSetContextCreate(CurrentMemoryContext,
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"HashTableContext",
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ALLOCSET_DEFAULT_SIZES);
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hashtable->batchCxt=AllocSetContextCreate(hashtable->hashCxt,
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"HashBatchContext",
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ALLOCSET_DEFAULT_SIZES);
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/* Allocate data that will live for the life of the hashjoin */
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oldcxt=MemoryContextSwitchTo(hashtable->hashCxt);
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if (nbatch>1)
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{
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/*

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