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If a database file with the WAL flag set is opened in exclusive-locking mode, use heap memory to store the wal-index instead of shared-memory.

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FossilOrigin-Name: 8dd5c69198619866923c6053b71899c1fb8c4c67
This commit is contained in:
dan
2010-11-01 17:38:24 +00:00
parent b6e321c09a
commit 8c40800439
12 changed files with 366 additions and 62 deletions
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78
src/pager.c
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@@ -1050,7 +1050,7 @@ static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
static int pagerUnlockDb(Pager *pPager, int eLock){
int rc = SQLITE_OK;
assert( !pPager->exclusiveMode );
assert( !pPager->exclusiveMode || pPager->eLock==eLock );
assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
if( isOpen(pPager->fd) ){
@@ -6350,7 +6350,8 @@ int sqlite3PagerLockingMode(Pager *pPager, int eMode){
|| eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_QUERY<0 );
assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
if( eMode>=0 && !pPager->tempFile ){
assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
pPager->exclusiveMode = (u8)eMode;
}
return (int)pPager->exclusiveMode;
@@ -6537,9 +6538,61 @@ int sqlite3PagerWalCallback(Pager *pPager){
*/
int sqlite3PagerWalSupported(Pager *pPager){
const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
return pMethods->iVersion>=2 && pMethods->xShmMap!=0;
return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
}
/*
** Attempt to take an exclusive lock on the database file. If a PENDING lock
** is obtained instead, immediately release it.
*/
static int pagerExclusiveLock(Pager *pPager){
int rc; /* Return code */
assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
/* If the attempt to grab the pending lock failed, release the
** exclusive lock that may have been obtained instead. */
pagerUnlockDb(pPager, SHARED_LOCK);
}
return rc;
}
/*
** Call sqlite3WalOpen() to open the WAL handle. If the pager is in
** exclusive-locking mode when this function is called, take an EXCLUSIVE
** lock on the database file and use heap-memory to store the wal-index
** in. Otherwise, use the normal shared-memory.
*/
static int pagerOpenWal(Pager *pPager){
int rc = SQLITE_OK;
assert( pPager->pWal==0 && pPager->tempFile==0 );
assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
/* If the pager is already in exclusive-mode, the WAL module will use
** heap-memory for the wal-index instead of the VFS shared-memory
** implementation. Take the exclusive lock now, before opening the WAL
** file, to make sure this is safe.
*/
if( pPager->exclusiveMode ){
rc = pagerExclusiveLock(pPager);
}
/* Open the connection to the log file. If this operation fails,
** (e.g. due to malloc() failure), return an error code.
*/
if( rc==SQLITE_OK ){
rc = sqlite3WalOpen(pPager->pVfs,
pPager->fd, pPager->zWal, pPager->exclusiveMode, &pPager->pWal
);
}
return rc;
}
/*
** The caller must be holding a SHARED lock on the database file to call
** this function.
@@ -6573,11 +6626,7 @@ int sqlite3PagerOpenWal(
/* Close any rollback journal previously open */
sqlite3OsClose(pPager->jfd);
/* Open the connection to the log file. If this operation fails,
** (e.g. due to malloc() failure), unlock the database file and
** return an error code.
*/
rc = sqlite3WalOpen(pPager->pVfs, pPager->fd, pPager->zWal, &pPager->pWal);
rc = pagerOpenWal(pPager);
if( rc==SQLITE_OK ){
pPager->journalMode = PAGER_JOURNALMODE_WAL;
pPager->eState = PAGER_OPEN;
@@ -6616,8 +6665,7 @@ int sqlite3PagerCloseWal(Pager *pPager){
);
}
if( rc==SQLITE_OK && logexists ){
rc = sqlite3WalOpen(pPager->pVfs, pPager->fd,
pPager->zWal, &pPager->pWal);
rc = pagerOpenWal(pPager);
}
}
@@ -6625,17 +6673,13 @@ int sqlite3PagerCloseWal(Pager *pPager){
** the database file, the log and log-summary files will be deleted.
*/
if( rc==SQLITE_OK && pPager->pWal ){
rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
rc = pagerExclusiveLock(pPager);
if( rc==SQLITE_OK ){
rc = sqlite3WalClose(pPager->pWal,
(pPager->noSync ? 0 : pPager->sync_flags),
pPager->pageSize, (u8*)pPager->pTmpSpace
(pPager->noSync ? 0 : pPager->sync_flags),
pPager->pageSize, (u8*)pPager->pTmpSpace
);
pPager->pWal = 0;
}else{
/* If we cannot get an EXCLUSIVE lock, downgrade the PENDING lock
** that we did get back to SHARED. */
pagerUnlockDb(pPager, SQLITE_LOCK_SHARED);
}
}
return rc;