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If a rollback mode transaction reduces the size of the database file, avoid actually truncating the file until after the transaction has been committed (but before the db has been unlocked). This means pages that are removed from the database by truncating the file need not be journalled.

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FossilOrigin-Name: b73847f17b7ae1298dfc52de6c4c4bc809bc77a3
This commit is contained in:
dan
2013-02-23 16:40:46 +00:00
parent f38b65a85d
commit bc1a3c6ce2
7 changed files with 89 additions and 81 deletions
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59
src/btree.c
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@@ -2595,6 +2595,7 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
goto trans_begun;
}
assert( pBt->bDoTruncate==0 );
/* Write transactions are not possible on a read-only database */
if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
@@ -3003,10 +3004,7 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
}while( bCommit && iFreePg>nFin );
assert( iFreePg<iLastPg );
rc = sqlite3PagerWrite(pLastPg->pDbPage);
if( rc==SQLITE_OK ){
rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, nFin!=0);
}
rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, nFin!=0);
releasePage(pLastPg);
if( rc!=SQLITE_OK ){
return rc;
@@ -3015,23 +3013,10 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
}
if( bCommit==0 ){
iLastPg--;
while( iLastPg==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, iLastPg) ){
if( PTRMAP_ISPAGE(pBt, iLastPg) ){
MemPage *pPg;
rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pPg->pDbPage);
releasePage(pPg);
if( rc!=SQLITE_OK ){
return rc;
}
}
do {
iLastPg--;
}
sqlite3PagerTruncateImage(pBt->pPager, iLastPg);
}while( iLastPg==PENDING_BYTE_PAGE(pBt) || PTRMAP_ISPAGE(pBt, iLastPg) );
pBt->bDoTruncate = 1;
pBt->nPage = iLastPg;
}
return SQLITE_OK;
@@ -3141,7 +3126,7 @@ static int autoVacuumCommit(BtShared *pBt){
put4byte(&pBt->pPage1->aData[32], 0);
put4byte(&pBt->pPage1->aData[36], 0);
put4byte(&pBt->pPage1->aData[28], nFin);
sqlite3PagerTruncateImage(pBt->pPager, nFin);
pBt->bDoTruncate = 1;
pBt->nPage = nFin;
}
if( rc!=SQLITE_OK ){
@@ -3196,6 +3181,9 @@ int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zMaster){
return rc;
}
}
if( pBt->bDoTruncate ){
sqlite3PagerTruncateImage(pBt->pPager, pBt->nPage);
}
#endif
rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zMaster, 0);
sqlite3BtreeLeave(p);
@@ -3211,6 +3199,9 @@ static void btreeEndTransaction(Btree *p){
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->bDoTruncate = 0;
#endif
btreeClearHasContent(pBt);
if( p->inTrans>TRANS_NONE && p->db->activeVdbeCnt>1 ){
/* If there are other active statements that belong to this database
@@ -5121,8 +5112,26 @@ static int allocateBtreePage(
pPrevTrunk = 0;
}while( searchList );
}else{
/* There are no pages on the freelist, so create a new page at the
** end of the file */
/* There are no pages on the freelist, so append a new page to the
** database image.
**
** Normally, new pages allocated by this block can be requested from the
** pager layer with the 'no-content' flag set. This prevents the pager
** from trying to read the pages content from disk. However, if the
** current transaction has already run one or more incremental-vacuum
** steps, then the page we are about to allocate may contain content
** that is required in the event of a rollback. In this case, do
** not set the no-content flag. This causes the pager to load and journal
** the current page content before overwriting it.
**
** Note that the pager will not actually attempt to load or journal
** content for any page that really does lie past the end of the database
** file on disk. So the effects of disabling the no-content optimization
** here are confined to those pages that lie between the end of the
** database image and the end of the database file.
*/
int bNoContent = (0==pBt->bDoTruncate);
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc ) return rc;
pBt->nPage++;
@@ -5137,7 +5146,7 @@ static int allocateBtreePage(
MemPage *pPg = 0;
TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetPage(pBt, pBt->nPage, &pPg, 1);
rc = btreeGetPage(pBt, pBt->nPage, &pPg, bNoContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pPg->pDbPage);
releasePage(pPg);
@@ -5151,7 +5160,7 @@ static int allocateBtreePage(
*pPgno = pBt->nPage;
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetPage(pBt, *pPgno, ppPage, 1);
rc = btreeGetPage(pBt, *pPgno, ppPage, bNoContent);
if( rc ) return rc;
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){