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Do create, open, or initialize the rollback journal until something actually

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needs to be written into the journal.  That way, expensive filesystem
operations are avoided if the transaction ends up being a no-op.

FossilOrigin-Name: b78e58ae1570ab4d66a69db445a752c6456038a0
This commit is contained in:
drh
2010-03-19 15:48:13 +00:00
parent 3b6f4c06ac
commit ba726f4939
5 changed files with 47 additions and 31 deletions
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34
src/pager.c
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@@ -1315,11 +1315,11 @@ static int pager_end_transaction(Pager *pPager, int hasMaster){
sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
#endif
sqlite3PcacheCleanAll(pPager->pPCache);
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
pPager->nRec = 0;
}
sqlite3PcacheCleanAll(pPager->pPCache);
if( !pPager->exclusiveMode ){
rc2 = osUnlock(pPager->fd, SHARED_LOCK);
@@ -4106,12 +4106,11 @@ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
}
}
/* If the required locks were successfully obtained, open the journal
** file and write the first journal-header to it.
/* No need to open the journal file at this time. It will be
** opened before it is written to. If we defer opening the journal,
** we might save the work of creating a file if the transaction
** ends up being a no-op.
*/
if( rc==SQLITE_OK && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
rc = pager_open_journal(pPager);
}
}else if( isOpen(pPager->jfd) && pPager->journalOff==0 ){
/* This happens when the pager was in exclusive-access mode the last
** time a (read or write) transaction was successfully concluded
@@ -4126,7 +4125,6 @@ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
}
PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
assert( !isOpen(pPager->jfd) || pPager->journalOff>0 || rc!=SQLITE_OK );
if( rc!=SQLITE_OK ){
assert( !pPager->dbModified );
/* Ignore any IO error that occurs within pager_end_transaction(). The
@@ -4182,11 +4180,11 @@ static int pager_write(PgHdr *pPg){
** or both.
**
** Higher level routines should have already started a transaction,
** which means they have acquired the necessary locks and opened
** a rollback journal. Double-check to makes sure this is the case.
** which means they have acquired the necessary locks but the rollback
** journal might not yet be open.
*/
rc = sqlite3PagerBegin(pPager, 0, pPager->subjInMemory);
if( NEVER(rc!=SQLITE_OK) ){
if( rc!=SQLITE_OK ){
return rc;
}
if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
@@ -4921,11 +4919,6 @@ int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
int ii; /* Iterator variable */
PagerSavepoint *aNew; /* New Pager.aSavepoint array */
/* Either there is no active journal or the sub-journal is open or
** the journal is always stored in memory */
assert( pPager->nSavepoint==0 || isOpen(pPager->sjfd) ||
pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
/* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
** if the allocation fails. Otherwise, zero the new portion in case a
** malloc failure occurs while populating it in the for(...) loop below.
@@ -4944,7 +4937,7 @@ int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
for(ii=nCurrent; ii<nSavepoint; ii++){
assert( pPager->dbSizeValid );
aNew[ii].nOrig = pPager->dbSize;
if( isOpen(pPager->jfd) && ALWAYS(pPager->journalOff>0) ){
if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
aNew[ii].iOffset = pPager->journalOff;
}else{
aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
@@ -5337,6 +5330,15 @@ int sqlite3PagerJournalMode(Pager *pPager, int eMode){
if( isOpen(pPager->jfd) ){
sqlite3OsClose(pPager->jfd);
}
assert( (PAGER_JOURNALMODE_TRUNCATE & 1)==1 );
assert( (PAGER_JOURNALMODE_PERSIST & 1)==1 );
assert( (PAGER_JOURNALMODE_DELETE & 1)==0 );
assert( (PAGER_JOURNALMODE_MEMORY & 1)==0 );
assert( (PAGER_JOURNALMODE_OFF & 1)==0 );
if( (pPager->journalMode & 1)==1 && (eMode & 1)==0
&& !pPager->exclusiveMode ){
sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
pPager->journalMode = (u8)eMode;
}
return (int)pPager->journalMode;