From 9e17bdb8a525ff89c4535cd153dc0f2fa813ea59 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 16 Mar 2018 16:03:45 -0400 Subject: [PATCH] Fix query-lifespan memory leakage in repeatedly executed hash joins. ExecHashTableCreate allocated some memory that wasn't freed by ExecHashTableDestroy, specifically the per-hash-key function information. That's not a huge amount of data, but if one runs a query that repeats a hash join enough times, it builds up. Fix by arranging for the data in question to be kept in the hashtable's hashCxt instead of leaving it "loose" in the query-lifespan executor context. (This ensures that we'll also clean up anything that the hash functions allocate in fn_mcxt.) Per report from Amit Khandekar. It's been like this forever, so back-patch to all supported branches. Discussion: https://postgr.es/m/CAJ3gD9cFofAWGvcxLOxDHC=B0hjtW8yGmUsF2hdGh97CM38=7g@mail.gmail.com --- src/backend/executor/nodeHash.c | 35 +++++++++++++++++---------------- 1 file changed, 18 insertions(+), 17 deletions(-) diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c index 06bb44b163..4f069d17fd 100644 --- a/src/backend/executor/nodeHash.c +++ b/src/backend/executor/nodeHash.c @@ -472,7 +472,8 @@ ExecHashTableCreate(HashState *state, List *hashOperators, bool keepNulls) * Initialize the hash table control block. * * The hashtable control block is just palloc'd from the executor's - * per-query memory context. + * per-query memory context. Everything else should be kept inside the + * subsidiary hashCxt or batchCxt. */ hashtable = (HashJoinTable) palloc(sizeof(HashJoinTableData)); hashtable->nbuckets = nbuckets; @@ -514,6 +515,22 @@ ExecHashTableCreate(HashState *state, List *hashOperators, bool keepNulls) hashtable, nbatch, nbuckets); #endif + /* + * Create temporary memory contexts in which to keep the hashtable working + * storage. See notes in executor/hashjoin.h. + */ + hashtable->hashCxt = AllocSetContextCreate(CurrentMemoryContext, + "HashTableContext", + ALLOCSET_DEFAULT_SIZES); + + hashtable->batchCxt = AllocSetContextCreate(hashtable->hashCxt, + "HashBatchContext", + ALLOCSET_DEFAULT_SIZES); + + /* Allocate data that will live for the life of the hashjoin */ + + oldcxt = MemoryContextSwitchTo(hashtable->hashCxt); + /* * Get info about the hash functions to be used for each hash key. Also * remember whether the join operators are strict. @@ -540,22 +557,6 @@ ExecHashTableCreate(HashState *state, List *hashOperators, bool keepNulls) i++; } - /* - * Create temporary memory contexts in which to keep the hashtable working - * storage. See notes in executor/hashjoin.h. - */ - hashtable->hashCxt = AllocSetContextCreate(CurrentMemoryContext, - "HashTableContext", - ALLOCSET_DEFAULT_SIZES); - - hashtable->batchCxt = AllocSetContextCreate(hashtable->hashCxt, - "HashBatchContext", - ALLOCSET_DEFAULT_SIZES); - - /* Allocate data that will live for the life of the hashjoin */ - - oldcxt = MemoryContextSwitchTo(hashtable->hashCxt); - if (nbatch > 1 && hashtable->parallel_state == NULL) { /* -- 2.40.0