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Only open a read-only connection to shared-memory if the "readonly_shm=1" option is specified as part of the database file URI (and if a read-write connection fails).

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FossilOrigin-Name: 671ba5fc59f7a958e5a4138d2425b1173a442ad7
This commit is contained in:
dan
2011-05-11 14:57:33 +00:00
parent 4edc6bf3ee
commit b6d2f9c5ef
11 changed files with 61 additions and 33 deletions
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14
src/wal.c
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@@ -529,7 +529,8 @@ static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ,
pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
);
if( rc==SQLITE_CANTOPEN && iPage==0 ){
if( rc==SQLITE_CANTOPEN && pWal->readOnlyShm>1 ){
assert( iPage==0 );
sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)1);
rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ,
pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
@@ -541,9 +542,10 @@ static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
}
}
}
*ppPage = pWal->apWiData[iPage];
assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
if( pWal->readOnlyShm>1 ) pWal->readOnlyShm = 0;
return rc;
}
@@ -1909,6 +1911,7 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
return rc;
};
assert( page0 || pWal->writeLock==0 );
assert( pWal->readOnlyShm==0 || pWal->readOnlyShm==1 );
/* If the first page of the wal-index has been mapped, try to read the
** wal-index header immediately, without holding any lock. This usually
@@ -2200,13 +2203,18 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
** Pager layer will use this to know that is cache is stale and
** needs to be flushed.
*/
int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
int sqlite3WalBeginReadTransaction(Wal *pWal, int readOnlyShm, int *pChanged){
int rc; /* Return code */
int cnt = 0; /* Number of TryBeginRead attempts */
if( pWal->nWiData==0 || pWal->apWiData[0]==0 ){
assert( readOnlyShm==0 || readOnlyShm==1 );
pWal->readOnlyShm = readOnlyShm*2;
}
do{
rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
}while( rc==WAL_RETRY );
assert( rc || pWal->readOnlyShm==0 || (readOnlyShm && pWal->readOnlyShm==1) );
testcase( (rc&0xff)==SQLITE_BUSY );
testcase( (rc&0xff)==SQLITE_IOERR );
testcase( rc==SQLITE_PROTOCOL );