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Commit0588ee6

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Include chunk overhead in hash table entry size estimate.
Don't try to be precise about it, just use a constant 16 bytes ofchunk overhead. Being smarter would require knowing the memory contextwhere the chunk will be allocated, which is not known by all callers.Discussion:https://postgr.es/m/20200325220936.il3ni2fj2j2b45y5@alap3.anarazel.de
1 parent3e0d80f commit0588ee6

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2 files changed

+31
-7
lines changed

2 files changed

+31
-7
lines changed

‎src/backend/executor/nodeAgg.c

Lines changed: 30 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -297,6 +297,12 @@
297297
/* minimum number of initial hash table buckets */
298298
#defineHASHAGG_MIN_BUCKETS 256
299299

300+
/*
301+
* Estimate chunk overhead as a constant 16 bytes. XXX: should this be
302+
* improved?
303+
*/
304+
#defineCHUNKHDRSZ 16
305+
300306
/*
301307
* Track all tapes needed for a HashAgg that spills. We don't know the maximum
302308
* number of tapes needed at the start of the algorithm (because it can
@@ -1639,14 +1645,32 @@ find_hash_columns(AggState *aggstate)
16391645
* Estimate per-hash-table-entry overhead.
16401646
*/
16411647
Size
1642-
hash_agg_entry_size(intnumAggs,SizetupleWidth,SizetransitionSpace)
1648+
hash_agg_entry_size(intnumTrans,SizetupleWidth,SizetransitionSpace)
16431649
{
1650+
SizetupleChunkSize;
1651+
SizepergroupChunkSize;
1652+
SizetransitionChunkSize;
1653+
SizetupleSize= (MAXALIGN(SizeofMinimalTupleHeader)+
1654+
tupleWidth);
1655+
SizepergroupSize=numTrans*sizeof(AggStatePerGroupData);
1656+
1657+
tupleChunkSize=CHUNKHDRSZ+tupleSize;
1658+
1659+
if (pergroupSize>0)
1660+
pergroupChunkSize=CHUNKHDRSZ+pergroupSize;
1661+
else
1662+
pergroupChunkSize=0;
1663+
1664+
if (transitionSpace>0)
1665+
transitionChunkSize=CHUNKHDRSZ+transitionSpace;
1666+
else
1667+
transitionChunkSize=0;
1668+
16441669
return
1645-
MAXALIGN(SizeofMinimalTupleHeader)+
1646-
MAXALIGN(tupleWidth)+
1647-
MAXALIGN(sizeof(TupleHashEntryData)+
1648-
numAggs*sizeof(AggStatePerGroupData))+
1649-
transitionSpace;
1670+
sizeof(TupleHashEntryData)+
1671+
tupleChunkSize+
1672+
pergroupChunkSize+
1673+
transitionChunkSize;
16501674
}
16511675

16521676
/*

‎src/include/executor/nodeAgg.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -314,7 +314,7 @@ extern AggState *ExecInitAgg(Agg *node, EState *estate, int eflags);
314314
externvoidExecEndAgg(AggState*node);
315315
externvoidExecReScanAgg(AggState*node);
316316

317-
externSizehash_agg_entry_size(intnumAggs,SizetupleWidth,
317+
externSizehash_agg_entry_size(intnumTrans,SizetupleWidth,
318318
SizetransitionSpace);
319319
externvoidhash_agg_set_limits(doublehashentrysize,uint64input_groups,
320320
intused_bits,Size*mem_limit,

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