diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/wal.c | 10 |
1 files changed, 9 insertions, 1 deletions
@@ -2210,6 +2210,14 @@ static int walBeginUnlocked(Wal *pWal, int *pChanged){ /* Try to map the *-shm file again. If it succeeds this time, then ** a non-readonly_shm connection has already connected to the database. ** In this case, start over with opening the transaction. + ** + ** The *-shm file was opened read-only, so sqlite3OsShmMap() can never + ** return SQLITE_OK here, as that would imply that it had established + ** a read/write mapping. A return of SQLITE_READONLY means success - that + ** a mapping has been established to a shared-memory segment that is actively + ** maintained by a writer. SQLITE_READONLY_CANTINIT means that all + ** all connections to the -shm file are read-only and hence the content + ** of the -shm file might be out-of-date. ** ** The WAL_READ_LOCK(0) lock held by this client prevents a checkpoint ** from taking place. But it does not prevent the wal from being wrapped @@ -2219,8 +2227,8 @@ static int walBeginUnlocked(Wal *pWal, int *pChanged){ ** the unlocked transaction, as the other client may overwrite wal ** frames that this client is still using. */ rc = sqlite3OsShmMap(pWal->pDbFd, 0, WALINDEX_PGSZ, 0, &pDummy); + assert( rc!=SQLITE_OK ); /* SQLITE_OK not possible for read-only connection */ if( rc!=SQLITE_READONLY_CANTINIT ){ - assert( rc!=SQLITE_OK ); rc = (rc==SQLITE_READONLY ? WAL_RETRY : rc); goto begin_unlocked_out; } |