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Commitb4e0741

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Avoid re-checking for visibility map extension too frequently.
When testing bits (but not when setting or clearing them), we nowwon't check whether the map has been extended. This significantlyimproves performance in the case where the visibility map doesn'texist yet, by avoiding an extra system call per tuple. To makesure backends notice eventually, send an smgr inval on VM extension.Dean Rasheed, with minor modifications by me.
1 parent8a02339 commitb4e0741

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+20
-5
lines changed

1 file changed

+20
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lines changed

‎src/backend/access/heap/visibilitymap.c

Lines changed: 20 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -88,6 +88,7 @@
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#include"storage/bufmgr.h"
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#include"storage/lmgr.h"
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#include"storage/smgr.h"
91+
#include"utils/inval.h"
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/*#define TRACE_VISIBILITYMAP */
@@ -482,16 +483,20 @@ vm_readbuf(Relation rel, BlockNumber blkno, bool extend)
482483
{
483484
Bufferbuf;
484485

486+
/*
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* We might not have opened the relation at the smgr level yet, or we might
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* have been forced to close it by a sinval message. The code below won't
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* necessarily notice relation extension immediately when extend = false,
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* so we rely on sinval messages to ensure that our ideas about the size of
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* the map aren't too far out of date.
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*/
485493
RelationOpenSmgr(rel);
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/*
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* If we haven't cached the size of the visibility map fork yet, check it
489-
* first. Also recheck if the requested block seems to be past end, since
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* our cached value might be stale. (We send smgr inval messages on
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* truncation, but not on extension.)
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* first.
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*/
493-
if (rel->rd_smgr->smgr_vm_nblocks==InvalidBlockNumber||
494-
blkno >=rel->rd_smgr->smgr_vm_nblocks)
499+
if (rel->rd_smgr->smgr_vm_nblocks==InvalidBlockNumber)
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{
496501
if (smgrexists(rel->rd_smgr,VISIBILITYMAP_FORKNUM))
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rel->rd_smgr->smgr_vm_nblocks=smgrnblocks(rel->rd_smgr,
@@ -560,13 +565,23 @@ vm_extend(Relation rel, BlockNumber vm_nblocks)
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vm_nblocks_now=smgrnblocks(rel->rd_smgr,VISIBILITYMAP_FORKNUM);
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568+
/* Now extend the file */
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while (vm_nblocks_now<vm_nblocks)
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{
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smgrextend(rel->rd_smgr,VISIBILITYMAP_FORKNUM,vm_nblocks_now,
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(char*)pg, false);
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vm_nblocks_now++;
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}
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/*
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* Send a shared-inval message to force other backends to close any smgr
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* references they may have for this rel, which we are about to change.
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* This is a useful optimization because it means that backends don't have
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* to keep checking for creation or extension of the file, which happens
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* infrequently.
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*/
583+
CacheInvalidateSmgr(rel->rd_smgr->smgr_rnode);
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570585
/* Update local cache with the up-to-date size */
571586
rel->rd_smgr->smgr_vm_nblocks=vm_nblocks_now;
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