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Fix possible "invalid memory alloc request size" failure in nodeHash.c.

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Limit the size of the hashtable pointer array to not more than
MaxAllocSize.  We've seen reports of failures due to this in HEAD/9.5,
and it seems possible in older branches as well.  The change in
NTUP_PER_BUCKET in 9.5 may have made the problem more likely, but
surely it didn't introduce it.

Tomas Vondra, slightly modified by me
This commit is contained in:
Tom Lane 2015-10-04 14:16:59 -04:00
parent 0f6a046b67
commit 45dd7cdbab
1 changed files with 4 additions and 2 deletions
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6
src/backend/executor/nodeHash.c
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@ -460,10 +460,12 @@ ExecChooseHashTableSize(double ntuples, int tupwidth, bool useskew,
* Set nbuckets to achieve an average bucket load of NTUP_PER_BUCKET when * Set nbuckets to achieve an average bucket load of NTUP_PER_BUCKET when
* memory is filled. Set nbatch to the smallest power of 2 that appears * memory is filled. Set nbatch to the smallest power of 2 that appears
* sufficient. The Min() steps limit the results so that the pointer * sufficient. The Min() steps limit the results so that the pointer
* arrays we'll try to allocate do not exceed work_mem. * arrays we'll try to allocate do not exceed work_mem nor MaxAllocSize.
*/ */
max_pointers = (work_mem * 1024L) / sizeof(void *); max_pointers = (work_mem * 1024L) / sizeof(HashJoinTuple);
max_pointers = Min(max_pointers, MaxAllocSize / sizeof(HashJoinTuple));
/* also ensure we avoid integer overflow in nbatch and nbuckets */ /* also ensure we avoid integer overflow in nbatch and nbuckets */
/* (this step is redundant given the current value of MaxAllocSize) */
max_pointers = Min(max_pointers, INT_MAX / 2); max_pointers = Min(max_pointers, INT_MAX / 2);
if (inner_rel_bytes > hash_table_bytes) if (inner_rel_bytes > hash_table_bytes)