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| author | Jeff Davis <jdavis@postgresql.org> | 2020-04-03 19:52:16 -0700 |
|---|---|---|
| committer | Jeff Davis <jdavis@postgresql.org> | 2020-04-03 20:07:58 -0700 |
| commit | 0588ee63aa2d8c5765d086991555cd9acdd4d86f (patch) | |
| tree | 6992318ae8adc1e241c73f063b55f61203daa136 /src/backend/executor/nodeAgg.c | |
| parent | 3e0d80fd8d3dd4f999e0d3aa3e591f480d8ad1fd (diff) | |
| download | postgresql-0588ee63aa2d8c5765d086991555cd9acdd4d86f.tar.gz postgresql-0588ee63aa2d8c5765d086991555cd9acdd4d86f.zip | |
Include chunk overhead in hash table entry size estimate.
Don't try to be precise about it, just use a constant 16 bytes of
chunk overhead. Being smarter would require knowing the memory context
where the chunk will be allocated, which is not known by all callers.
Discussion: https://postgr.es/m/20200325220936.il3ni2fj2j2b45y5@alap3.anarazel.de
Diffstat (limited to 'src/backend/executor/nodeAgg.c')
| -rw-r--r-- | src/backend/executor/nodeAgg.c | 36 |
1 files changed, 30 insertions, 6 deletions
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c index 4c8c5cfc07a..4e100e5755f 100644 --- a/src/backend/executor/nodeAgg.c +++ b/src/backend/executor/nodeAgg.c @@ -298,6 +298,12 @@ #define HASHAGG_MIN_BUCKETS 256 /* + * Estimate chunk overhead as a constant 16 bytes. XXX: should this be + * improved? + */ +#define CHUNKHDRSZ 16 + +/* * Track all tapes needed for a HashAgg that spills. We don't know the maximum * number of tapes needed at the start of the algorithm (because it can * recurse), so one tape set is allocated and extended as needed for new @@ -1639,14 +1645,32 @@ find_hash_columns(AggState *aggstate) * Estimate per-hash-table-entry overhead. */ Size -hash_agg_entry_size(int numAggs, Size tupleWidth, Size transitionSpace) +hash_agg_entry_size(int numTrans, Size tupleWidth, Size transitionSpace) { + Size tupleChunkSize; + Size pergroupChunkSize; + Size transitionChunkSize; + Size tupleSize = (MAXALIGN(SizeofMinimalTupleHeader) + + tupleWidth); + Size pergroupSize = numTrans * sizeof(AggStatePerGroupData); + + tupleChunkSize = CHUNKHDRSZ + tupleSize; + + if (pergroupSize > 0) + pergroupChunkSize = CHUNKHDRSZ + pergroupSize; + else + pergroupChunkSize = 0; + + if (transitionSpace > 0) + transitionChunkSize = CHUNKHDRSZ + transitionSpace; + else + transitionChunkSize = 0; + return - MAXALIGN(SizeofMinimalTupleHeader) + - MAXALIGN(tupleWidth) + - MAXALIGN(sizeof(TupleHashEntryData) + - numAggs * sizeof(AggStatePerGroupData)) + - transitionSpace; + sizeof(TupleHashEntryData) + + tupleChunkSize + + pergroupChunkSize + + transitionChunkSize; } /* |