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Commitc6e394c

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Small improvements for allocation logic in ginHeapTupleFastCollect().
Avoid repetitive calls to repalloc() when the required size of thecollector array grows more than 2x in one call. Also ensure that thearray size is a power of 2 (since palloc will probably consume a powerof 2 anyway) and doesn't start out very small (which'd likely just leadto extra repallocs).David Rowley, tweaked a bit by meDiscussion:https://postgr.es/m/CAKJS1f8vn-iSBE8PKeVHrnhvyjRNYCxguPFFY08QLYmjWG9hPQ@mail.gmail.com
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‎src/backend/access/gin/ginfast.c

Lines changed: 27 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -486,18 +486,41 @@ ginHeapTupleFastCollect(GinState *ginstate,
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entries=ginExtractEntries(ginstate,attnum,value,isNull,
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&nentries,&categories);
488488

489+
/*
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* Protect against integer overflow in allocation calculations
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*/
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if (nentries<0||
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collector->ntuples+nentries>MaxAllocSize /sizeof(IndexTuple))
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elog(ERROR,"too many entries for GIN index");
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/*
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* Allocate/reallocate memory for storing collected tuples
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*/
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if (collector->tuples==NULL)
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{
494-
collector->lentuples=nentries*ginstate->origTupdesc->natts;
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/*
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* Determine the number of elements to allocate in the tuples array
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* initially. Make it a power of 2 to avoid wasting memory when
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* resizing (since palloc likes powers of 2).
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*/
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collector->lentuples=16;
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while (collector->lentuples<nentries)
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collector->lentuples *=2;
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collector->tuples= (IndexTuple*)palloc(sizeof(IndexTuple)*collector->lentuples);
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}
497-
498-
while (collector->ntuples+nentries>collector->lentuples)
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elseif (collector->lentuples<collector->ntuples+nentries)
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{
500-
collector->lentuples *=2;
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/*
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* Advance lentuples to the next suitable power of 2. This won't
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* overflow, though we could get to a value that exceeds
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* MaxAllocSize/sizeof(IndexTuple), causing an error in repalloc.
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*/
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do
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{
521+
collector->lentuples *=2;
522+
}while (collector->lentuples<collector->ntuples+nentries);
523+
501524
collector->tuples= (IndexTuple*)repalloc(collector->tuples,
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sizeof(IndexTuple)*collector->lentuples);
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}

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