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Commitbbaf315

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Add bound check before bsearch() for performance
In the current lazy vacuum implementation, some index AMs such asbtree indexes call lazy_tid_reaped() for each index tuple duringambulkdelete to check if the index tuple points to the (collected)garbage tuple. In that function, we simply call bsearch(), but weshould be able to know the result without bsearch() if the index tuplepoints to the heap tuple that is out of range of the collected garbagetuples. Therefore, add a simple bound check before resorting tobsearch(). Testing has shown that this can give significantperformance benefits.Author: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>Discussion:https://www.postgresql.org/message-id/flat/CA+fd4k76j8jKzJzcx8UqEugvayaMSnQz0iLUt_XgBp-_-bd22A@mail.gmail.com
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‎src/backend/access/heap/vacuumlazy.c

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@@ -61,6 +61,7 @@
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#include"access/visibilitymap.h"
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#include"access/xact.h"
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#include"access/xlog.h"
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#include"catalog/index.h"
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#include"catalog/storage.h"
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#include"commands/dbcommands.h"
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#include"commands/progress.h"
@@ -2923,8 +2924,24 @@ static bool
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lazy_tid_reaped(ItemPointeritemptr,void*state)
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{
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LVDeadTuples*dead_tuples= (LVDeadTuples*)state;
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int64litem,
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ritem,
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item;
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ItemPointerres;
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litem=itemptr_encode(&dead_tuples->itemptrs[0]);
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ritem=itemptr_encode(&dead_tuples->itemptrs[dead_tuples->num_tuples-1]);
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item=itemptr_encode(itemptr);
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/*
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* Doing a simple bound check before bsearch() is useful to avoid the
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* extra cost of bsearch(), especially if dead tuples on the heap are
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* concentrated in a certain range. Since this function is called for
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* every index tuple, it pays to be really fast.
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*/
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if (item<litem||item>ritem)
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return false;
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res= (ItemPointer)bsearch((void*)itemptr,
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(void*)dead_tuples->itemptrs,
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dead_tuples->num_tuples,

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