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Commit626df47

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Remove 'additional' pointer from TupleHashEntryData.
Reduces memory required for hash aggregation by avoiding an allocationand a pointer in the TupleHashEntryData structure. That structure isused for all buckets, whether occupied or not, so the savings issubstantial.Discussion:https://postgr.es/m/AApHDvpN4v3t_sdz4dvrv1Fx_ZPw=twSnxuTEytRYP7LFz5K9A@mail.gmail.comReviewed-by: David Rowley <dgrowleyml@gmail.com>
1 parenta0942f4 commit626df47

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3 files changed

+16
-7
lines changed

3 files changed

+16
-7
lines changed

‎src/backend/executor/execGrouping.c

Lines changed: 12 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -485,11 +485,18 @@ LookupTupleHashEntry_internal(TupleHashTable hashtable, TupleTableSlot *slot,
485485

486486
MemoryContextSwitchTo(hashtable->tablecxt);
487487

488-
entry->firstTuple=ExecCopySlotMinimalTuple(slot);
489-
if (hashtable->additionalsize>0)
490-
entry->additional=palloc0(hashtable->additionalsize);
491-
else
492-
entry->additional=NULL;
488+
/*
489+
* Copy the first tuple into the table context, and request
490+
* additionalsize extra bytes before the allocation.
491+
*
492+
* The caller can get a pointer to the additional data with
493+
* TupleHashEntryGetAdditional(), and store arbitrary data there.
494+
* Placing both the tuple and additional data in the same
495+
* allocation avoids the need to store an extra pointer in
496+
* TupleHashEntryData or allocate an additional chunk.
497+
*/
498+
entry->firstTuple=ExecCopySlotMinimalTupleExtra(slot,
499+
hashtable->additionalsize);
493500
}
494501
}
495502
else

‎src/include/executor/executor.h

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -188,7 +188,10 @@ TupleHashEntryGetTuple(TupleHashEntry entry)
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staticinlinevoid*
189189
TupleHashEntryGetAdditional(TupleHashTablehashtable,TupleHashEntryentry)
190190
{
191-
returnentry->additional;
191+
if (hashtable->additionalsize>0)
192+
return (char*)entry->firstTuple-hashtable->additionalsize;
193+
else
194+
returnNULL;
192195
}
193196
#endif
194197

‎src/include/nodes/execnodes.h

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -840,7 +840,6 @@ typedef struct TupleHashTableData *TupleHashTable;
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typedefstructTupleHashEntryData
841841
{
842842
MinimalTuplefirstTuple;/* copy of first tuple in this group */
843-
void*additional;/* user data */
844843
uint32status;/* hash status */
845844
uint32hash;/* hash value (cached) */
846845
}TupleHashEntryData;

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