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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2022-08-13 16:59:58 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2022-08-13 16:59:58 -0400 |
| commit | aee95437362db0ef2c4caed942272c86b4509390 (patch) | |
| tree | 986f34da205213f230acfc1501c81e121748d26f | |
| parent | 00ac61695e5c7d573b14bb7a61387a3fae017928 (diff) | |
| download | postgresql-aee95437362db0ef2c4caed942272c86b4509390.tar.gz postgresql-aee95437362db0ef2c4caed942272c86b4509390.zip | |
Avoid misbehavior when hash_table_bytes < bucket_size.
It's possible to reach this case when work_mem is very small and tupsize
is (relatively) very large. In that case ExecChooseHashTableSize would
get an assertion failure, or with asserts off it'd compute nbuckets = 0,
which'd likely cause misbehavior later (I've not checked). To fix,
clamp the number of buckets to be at least 1.
This is due to faulty conversion of old my_log2() coding in 28d936031.
Back-patch to v13, as that was.
Zhang Mingli
Discussion: https://postgr.es/m/beb64ca0-91e2-44ac-bf4a-7ea36275ec02@Spark
| -rw-r--r-- | src/backend/executor/nodeHash.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c index 3510a4247c1..b052b3b0447 100644 --- a/src/backend/executor/nodeHash.c +++ b/src/backend/executor/nodeHash.c @@ -832,7 +832,10 @@ ExecChooseHashTableSize(double ntuples, int tupwidth, bool useskew, * overhead for the hash code, pointer to the next tuple, etc. */ bucket_size = (tupsize * NTUP_PER_BUCKET + sizeof(HashJoinTuple)); - sbuckets = pg_nextpower2_size_t(hash_table_bytes / bucket_size); + if (hash_table_bytes <= bucket_size) + sbuckets = 1; /* avoid pg_nextpower2_size_t(0) */ + else + sbuckets = pg_nextpower2_size_t(hash_table_bytes / bucket_size); sbuckets = Min(sbuckets, max_pointers); nbuckets = (int) sbuckets; nbuckets = pg_nextpower2_32(nbuckets); |