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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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67
src/pager.c
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@@ -1838,6 +1838,8 @@ static int pager_error(Pager *pPager, int rc){
return rc;
}
static int pager_truncate(Pager *pPager, Pgno nPage);
/*
** This routine ends a transaction. A transaction is usually ended by
** either a COMMIT or a ROLLBACK operation. This routine may be called
@@ -1891,7 +1893,7 @@ static int pager_error(Pager *pPager, int rc){
** to the first error encountered (the journal finalization one) is
** returned.
*/
static int pager_end_transaction(Pager *pPager, int hasMaster){
static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
int rc = SQLITE_OK; /* Error code from journal finalization operation */
int rc2 = SQLITE_OK; /* Error code from db file unlock operation */
@@ -1977,7 +1979,17 @@ static int pager_end_transaction(Pager *pPager, int hasMaster){
*/
rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
assert( rc2==SQLITE_OK );
}else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){
/* This branch is taken when committing a transaction in rollback-journal
** mode if the database file on disk is larger than the database image.
** At this point the journal has been finalized and the transaction
** successfully committed, but the EXCLUSIVE lock is still held on the
** file. So it is safe to truncate the database file to its minimum
** required size. */
assert( pPager->eLock==EXCLUSIVE_LOCK );
rc = pager_truncate(pPager, pPager->dbSize);
}
if( !pPager->exclusiveMode
&& (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
){
@@ -2016,7 +2028,7 @@ static void pagerUnlockAndRollback(Pager *pPager){
sqlite3EndBenignMalloc();
}else if( !pPager->exclusiveMode ){
assert( pPager->eState==PAGER_READER );
pager_end_transaction(pPager, 0);
pager_end_transaction(pPager, 0, 0);
}
}
pager_unlock(pPager);
@@ -2791,7 +2803,7 @@ end_playback:
rc = sqlite3PagerSync(pPager);
}
if( rc==SQLITE_OK ){
rc = pager_end_transaction(pPager, zMaster[0]!='\0');
rc = pager_end_transaction(pPager, zMaster[0]!='\0', 0);
testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK && zMaster[0] && res ){
@@ -5885,36 +5897,6 @@ int sqlite3PagerCommitPhaseOne(
#endif
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
/* If this transaction has made the database smaller, then all pages
** being discarded by the truncation must be written to the journal
** file.
**
** Before reading the pages with page numbers larger than the
** current value of Pager.dbSize, set dbSize back to the value
** that it took at the start of the transaction. Otherwise, the
** calls to sqlite3PagerGet() return zeroed pages instead of
** reading data from the database file.
*/
if( pPager->dbSize<pPager->dbOrigSize
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF
){
Pgno i; /* Iterator variable */
const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
const Pgno dbSize = pPager->dbSize; /* Database image size */
pPager->dbSize = pPager->dbOrigSize;
for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
PgHdr *pPage; /* Page to journal */
rc = sqlite3PagerGet(pPager, i, &pPage);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
rc = sqlite3PagerWrite(pPage);
sqlite3PagerUnref(pPage);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
}
}
pPager->dbSize = dbSize;
}
/* Write the master journal name into the journal file. If a master
** journal file name has already been written to the journal file,
** or if zMaster is NULL (no master journal), then this call is a no-op.
@@ -5942,11 +5924,14 @@ int sqlite3PagerCommitPhaseOne(
goto commit_phase_one_exit;
}
sqlite3PcacheCleanAll(pPager->pPCache);
/* If the file on disk is not the same size as the database image,
** then use pager_truncate to grow or shrink the file here.
*/
if( pPager->dbSize!=pPager->dbFileSize ){
/* If the file on disk is smaller than the database image, use
** pager_truncate to grow the file here. This can happen if the database
** image was extended as part of the current transaction and then the
** last page in the db image moved to the free-list. In this case the
** last page is never written out to disk, leaving the database file
** undersized. Fix this now if it is the case. */
if( pPager->dbSize>pPager->dbFileSize ){
Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
assert( pPager->eState==PAGER_WRITER_DBMOD );
rc = pager_truncate(pPager, nNew);
@@ -6019,7 +6004,7 @@ int sqlite3PagerCommitPhaseTwo(Pager *pPager){
}
PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
rc = pager_end_transaction(pPager, pPager->setMaster);
rc = pager_end_transaction(pPager, pPager->setMaster, 1);
return pager_error(pPager, rc);
}
@@ -6064,11 +6049,11 @@ int sqlite3PagerRollback(Pager *pPager){
if( pagerUseWal(pPager) ){
int rc2;
rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
rc2 = pager_end_transaction(pPager, pPager->setMaster);
rc2 = pager_end_transaction(pPager, pPager->setMaster, 0);
if( rc==SQLITE_OK ) rc = rc2;
}else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
int eState = pPager->eState;
rc = pager_end_transaction(pPager, 0);
rc = pager_end_transaction(pPager, 0, 0);
if( !MEMDB && eState>PAGER_WRITER_LOCKED ){
/* This can happen using journal_mode=off. Move the pager to the error
** state to indicate that the contents of the cache may not be trusted.