diff options
Diffstat (limited to 'src/wal.c')
| -rw-r--r-- | src/wal.c | 12 |
1 files changed, 7 insertions, 5 deletions
@@ -3138,17 +3138,20 @@ int sqlite3WalFindFrame( u32 *piRead /* OUT: Frame number (or zero) */ ){ u32 iRead = 0; /* If !=0, WAL frame to return data from */ - u32 iLast; /* Last page in WAL for this reader */ + u32 iLast = pWal->hdr.mxFrame; /* Last page in WAL for this reader */ int iHash; /* Used to loop through N hash tables */ int iMinHash; /* This routine is only be called from within a read transaction. */ assert( pWal->readLock>=0 || pWal->lockError ); - /* if pWal->readLock==0, then the WAL is ignored by the reader - ** so return early, as if the WAL were empty. + /* If the "last page" field of the wal-index header snapshot is 0, then + ** no data will be read from the wal under any circumstances. Return early + ** in this case as an optimization. Likewise, if pWal->readLock==0, + ** then the WAL is ignored by the reader so return early, as if the + ** WAL were empty. */ - if( pWal->readLock==0 && pWal->bShmUnreliable==0 ){ + if( iLast==0 || (pWal->readLock==0 && pWal->bShmUnreliable==0) ){ *piRead = 0; return SQLITE_OK; } @@ -3179,7 +3182,6 @@ int sqlite3WalFindFrame( ** table after the current read-transaction had started. */ iMinHash = walFramePage(pWal->minFrame); - iLast = pWal->hdr.mxFrame; for(iHash=walFramePage(iLast); iHash>=iMinHash; iHash--){ WalHashLoc sLoc; /* Hash table location */ int iKey; /* Hash slot index */ |