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Try to avoid reading pages when moving overflow chains to the free-list. (CVS 3886)

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FossilOrigin-Name: 8cccec68bd9073b2b19d3d31cf0b77b0ce76172e
This commit is contained in:
danielk1977
2007-04-30 16:55:00 +00:00
parent b4626a3e16
commit 8c0a959f35
3 changed files with 64 additions and 12 deletions
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62
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.361 2007/04/28 15:47:44 danielk1977 Exp $
** $Id: btree.c,v 1.362 2007/04/30 16:55:01 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -4046,6 +4046,60 @@ static int freePage(MemPage *pPage){
return rc;
}
/*
** Get a MemPage structure for overflow page number ovfl. If it
** is not zero, the page number of the overflow page following the
** one retrieved is written to *pPgnoNext.
**
** If it is possible to figure out the page-number of the next
** overflow page without reading the data of page ovfl, then
** sqlite3PagerAcquire() is passed the "noContent" flag when
** page ovfl is retrieved.
*/
static int getOverflowPage(
BtShared *pBt,
Pgno ovfl,
MemPage **ppPage,
Pgno *pPgnoNext
){
Pgno next = 0;
int rc;
if( !pPgnoNext ){
return getPage(pBt, ovfl, ppPage, 1);
}
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
Pgno pgno;
Pgno iGuess = ovfl+1;
u8 eType;
while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
iGuess++;
}
if( iGuess<sqlite3PagerPagecount(pBt->pPager) ){
rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
next = iGuess;
}
}
}
#endif
rc = getPage(pBt, ovfl, ppPage, 0);
if( rc==SQLITE_OK ){
assert(next==0 || next==get4byte((*ppPage)->aData));
next = get4byte((*ppPage)->aData);
}
*pPgnoNext = next;
return rc;
}
/*
** Free any overflow pages associated with the given Cell.
*/
@@ -4070,11 +4124,9 @@ static int clearCell(MemPage *pPage, unsigned char *pCell){
if( ovflPgno==0 || ovflPgno>sqlite3PagerPagecount(pBt->pPager) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getPage(pBt, ovflPgno, &pOvfl, nOvfl==0);
rc = getOverflowPage(pBt, ovflPgno, &pOvfl, (nOvfl==0)?0:&ovflPgno);
if( rc ) return rc;
if( nOvfl ){
ovflPgno = get4byte(pOvfl->aData);
}
rc = freePage(pOvfl);
sqlite3PagerUnref(pOvfl->pDbPage);
if( rc ) return rc;