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Pager optimization: do not write or journal free pages. This results in

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a 2x performance gain for large INSERTs and a 5x performance gain for
large DELETEs. (CVS 410)

FossilOrigin-Name: cf1ebcfb741786f84a596c406f4c492f68cbe881
This commit is contained in:
drh
2002-03-02 20:41:57 +00:00
parent f9ffac96a7
commit 30e58750c1
5 changed files with 132 additions and 21 deletions
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51
src/pager.c
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@@ -18,7 +18,7 @@
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.40 2002/02/19 13:39:22 drh Exp $
** @(#) $Id: pager.c,v 1.41 2002/03/02 20:41:59 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
@@ -1126,6 +1126,55 @@ int sqlitepager_iswriteable(void *pData){
return pPg->dirty;
}
/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page "pgno" back to the disk, even though
** that page might be marked as dirty.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused. The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlitepager_dont_rollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
*/
void sqlitepager_dont_write(Pager *pPager, Pgno pgno){
PgHdr *pPg;
pPg = pager_lookup(pPager, pgno);
if( pPg && pPg->dirty ){
pPg->dirty = 0;
}
}
/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page. This
** means that the pager does not have to record the given page in the
** rollback journal.
*/
void sqlitepager_dont_rollback(void *pData){
PgHdr *pPg = DATA_TO_PGHDR(pData);
Pager *pPager = pPg->pPager;
if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return;
if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){
assert( pPager->aInJournal!=0 );
pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->inJournal = 1;
if( pPager->ckptOpen ){
pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->inCkpt = 1;
}
}
if( pPager->ckptOpen && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
assert( pPager->aInCkpt!=0 );
pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->inCkpt = 1;
}
}
/*
** Commit all changes to the database and release the write lock.
**