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Changes so that WAL and exclusive-locking mode work together.

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FossilOrigin-Name: 71e7b1cf9f4cd02a2a9bc8a3e58acd7a7e3c7e60
This commit is contained in:
dan
2010-05-11 12:19:26 +00:00
parent a10069dd22
commit 5543759b1b
6 changed files with 321 additions and 35 deletions
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77
src/wal.c
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@@ -132,6 +132,7 @@ struct Wal {
u32 *pWiData; /* Pointer to wal-index content in memory */
u8 lockState; /* SQLITE_SHM_xxxx constant showing lock state */
u8 readerType; /* SQLITE_SHM_READ or SQLITE_SHM_READ_FULL */
u8 exclusiveMode; /* Non-zero if connection is in exclusive mode */
WalIndexHdr hdr; /* Wal-index for current snapshot */
char *zName; /* Name of underlying storage */
};
@@ -217,14 +218,17 @@ static void walChecksumBytes(u8 *aByte, int nByte, u32 *aCksum){
** in pWal->readerType.
*/
static int walSetLock(Wal *pWal, int desiredStatus){
int rc, got;
if( pWal->lockState==desiredStatus ) return SQLITE_OK;
got = pWal->lockState;
rc = pWal->pVfs->xShmLock(pWal->pVfs, pWal->pWIndex, desiredStatus, &got);
pWal->lockState = got;
if( got==SQLITE_SHM_READ_FULL || got==SQLITE_SHM_READ ){
pWal->readerType = got;
pWal->lockState = SQLITE_SHM_READ;
int rc = SQLITE_OK; /* Return code */
if( pWal->exclusiveMode || pWal->lockState==desiredStatus ){
pWal->lockState = desiredStatus;
}else{
int got = pWal->lockState;
rc = pWal->pVfs->xShmLock(pWal->pVfs, pWal->pWIndex, desiredStatus, &got);
pWal->lockState = got;
if( got==SQLITE_SHM_READ_FULL || got==SQLITE_SHM_READ ){
pWal->readerType = got;
pWal->lockState = SQLITE_SHM_READ;
}
}
return rc;
}
@@ -1231,7 +1235,7 @@ int sqlite3WalWriteLock(Wal *pWal, int op){
walSetLock(pWal, SQLITE_SHM_READ);
}
}
}else if( ALWAYS( pWal->lockState==SQLITE_SHM_WRITE ) ){
}else if( pWal->lockState==SQLITE_SHM_WRITE ){
rc = walSetLock(pWal, SQLITE_SHM_READ);
}
return rc;
@@ -1250,18 +1254,20 @@ int sqlite3WalWriteLock(Wal *pWal, int op){
** function returns SQLITE_OK.
*/
int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
int unused;
int rc;
Pgno iMax = pWal->hdr.iLastPg;
Pgno iFrame;
assert( pWal->pWiData==0 );
rc = walIndexReadHdr(pWal, &unused);
for(iFrame=pWal->hdr.iLastPg+1; rc==SQLITE_OK && iFrame<=iMax; iFrame++){
assert( pWal->lockState==SQLITE_SHM_WRITE );
rc = xUndo(pUndoCtx, pWal->pWiData[walIndexEntry(iFrame)]);
int rc = SQLITE_OK;
if( pWal->lockState==SQLITE_SHM_WRITE ){
int unused;
Pgno iMax = pWal->hdr.iLastPg;
Pgno iFrame;
assert( pWal->pWiData==0 );
rc = walIndexReadHdr(pWal, &unused);
for(iFrame=pWal->hdr.iLastPg+1; rc==SQLITE_OK && iFrame<=iMax; iFrame++){
assert( pWal->lockState==SQLITE_SHM_WRITE );
rc = xUndo(pUndoCtx, pWal->pWiData[walIndexEntry(iFrame)]);
}
walIndexUnmap(pWal);
}
walIndexUnmap(pWal);
return rc;
}
@@ -1500,4 +1506,35 @@ int sqlite3WalCallback(Wal *pWal){
}
return (int)ret;
}
/*
** This function is called to set or query the exclusive-mode flag
** associated with the WAL connection passed as the first argument. The
** exclusive-mode flag should be set to indicate that the caller is
** holding an EXCLUSIVE lock on the database file (it does this in
** locking_mode=exclusive mode). If the EXCLUSIVE lock is to be dropped,
** the flag set by this function should be cleared before doing so.
**
** The value of the exclusive-mode flag may only be modified when
** the WAL connection is in READ state.
**
** When the flag is set, this module does not call the VFS xShmLock()
** method to obtain any locks on the wal-index (as it assumes it
** has exclusive access to the wal and wal-index files anyhow). It
** continues to hold (and does not drop) the existing READ lock on
** the wal-index.
**
** To set or clear the flag, the "op" parameter is passed 1 or 0,
** respectively. To query the flag, pass -1. In all cases, the value
** returned is the value of the exclusive-mode flag (after its value
** has been modified, if applicable).
*/
int sqlite3WalExclusiveMode(Wal *pWal, int op){
if( op>=0 ){
assert( pWal->lockState==SQLITE_SHM_READ );
pWal->exclusiveMode = (u8)op;
}
return pWal->exclusiveMode;
}
#endif /* #ifndef SQLITE_OMIT_WAL */