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Add experimental locking scheme.

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FossilOrigin-Name: 3f958e87c33d667d299b03ffdef58db5dc6363f4
This commit is contained in:
dan
2010-04-13 19:27:31 +00:00
parent 622194c0d2
commit 64d039e512
5 changed files with 248 additions and 67 deletions
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49
src/pager.c
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@@ -3120,6 +3120,7 @@ static int pager_write_pagelist(PgHdr *pList){
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
assert( !pagerUseLog(pList->pPager) );
assert( pPager->state>=PAGER_RESERVED );
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
@@ -3785,21 +3786,13 @@ int sqlite3PagerSharedLock(Pager *pPager){
if( pagerUseLog(pPager) ){
int changed = 0;
/* TODO: Change the following block to grab a WAL read-lock. Or,
** combine obtaining the read-lock with LogOpenSnapshot()? */
rc = pager_wait_on_lock(pPager, SHARED_LOCK);
if( rc!=SQLITE_OK ){
assert( pPager->state==PAGER_UNLOCK );
return pager_error(pPager, rc);
}
rc = sqlite3LogOpenSnapshot(pPager->pLog, &changed);
if( rc==SQLITE_OK ){
if( changed ){
pager_reset(pPager);
assert( pPager->errCode || pPager->dbSizeValid==0 );
}
pPager->state = PAGER_SHARED;
pPager->state = PAGER_SHARED; /* TODO: Is this right? */
rc = sqlite3PagerPagecount(pPager, &changed);
}
}else if( pPager->state==PAGER_UNLOCK || isErrorReset ){
@@ -4330,20 +4323,7 @@ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
assert( pPager->pInJournal==0 );
assert( !MEMDB && !pPager->tempFile );
/* Obtain a RESERVED lock on the database file. If the exFlag parameter
** is true, then immediately upgrade this to an EXCLUSIVE lock. The
** busy-handler callback can be used when upgrading to the EXCLUSIVE
** lock, but not when obtaining the RESERVED lock.
*/
rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
if( rc==SQLITE_OK ){
pPager->state = PAGER_RESERVED;
if( exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
if( rc==SQLITE_OK && pagerUseLog(pPager) ){
if( pagerUseLog(pPager) ){
/* Grab the write lock on the log file. If successful, upgrade to
** PAGER_EXCLUSIVE state. Otherwise, return an error code to the caller.
** The busy-handler is not invoked if another connection already
@@ -4352,6 +4332,20 @@ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
rc = sqlite3LogWriteLock(pPager->pLog, 1);
if( rc==SQLITE_OK ){
pPager->dbOrigSize = pPager->dbSize;
pPager->state = PAGER_RESERVED;
}
}else{
/* Obtain a RESERVED lock on the database file. If the exFlag parameter
** is true, then immediately upgrade this to an EXCLUSIVE lock. The
** busy-handler callback can be used when upgrading to the EXCLUSIVE
** lock, but not when obtaining the RESERVED lock.
*/
rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
if( rc==SQLITE_OK ){
pPager->state = PAGER_RESERVED;
if( exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
}
@@ -5657,11 +5651,10 @@ sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
int sqlite3PagerCheckpoint(Pager *pPager){
int rc = SQLITE_OK;
if( pPager->pLog ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
if( rc==SQLITE_OK ){
u8 *zBuf = (u8 *)pPager->pTmpSpace;
rc = sqlite3LogCheckpoint(pPager->pLog, pPager->fd, zBuf);
}
u8 *zBuf = (u8 *)pPager->pTmpSpace;
rc = sqlite3LogCheckpoint(pPager->pLog, pPager->fd,
zBuf, pPager->xBusyHandler, pPager->pBusyHandlerArg
);
}
return rc;
}