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Avoid disk writes for read-only transactions.

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This commit is contained in:
Vadim B. Mikheev
1999-06-29 04:54:49 +00:00
parent cffd0f9c89
commit 49f68a8584
2 changed files with 49 additions and 29 deletions
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17
src/backend/storage/buffer/bufmgr.c
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@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.55 1999/06/11 09:00:02 vadim Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.56 1999/06/29 04:54:47 vadim Exp $
*
*-------------------------------------------------------------------------
*/
@ -78,6 +78,15 @@ extern long int LocalBufferHitCount;
extern long int BufferFlushCount;
extern long int LocalBufferFlushCount;
/*
* It's used to avoid disk writes for read-only transactions
* (i.e. when no one shared buffer was changed by transaction).
* We set it to true in WriteBuffer/WriteNoReleaseBuffer when
* marking shared buffer as dirty. We set it to false in xact.c
* after transaction is committed/aborted.
*/
bool SharedBufferChanged = false;
static int WriteMode = BUFFER_LATE_WRITE; /* Delayed write is
* default */
@ -699,6 +708,8 @@ WriteBuffer(Buffer buffer)
bufHdr = &BufferDescriptors[buffer - 1];
SharedBufferChanged = true;
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
@ -810,6 +821,8 @@ FlushBuffer(Buffer buffer, bool release)
bufrel = RelationIdCacheGetRelation(bufHdr->tag.relId.relId);
Assert(bufrel != (Relation) NULL);
SharedBufferChanged = true;
/* To check if block content changed while flushing. - vadim 01/17/97 */
SpinAcquire(BufMgrLock);
bufHdr->flags &= ~BM_JUST_DIRTIED;
@ -875,6 +888,8 @@ WriteNoReleaseBuffer(Buffer buffer)
bufHdr = &BufferDescriptors[buffer - 1];
SharedBufferChanged = true;
SpinAcquire(BufMgrLock);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
SpinRelease(BufMgrLock);