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version-3.42.1
src/wal.h
155 строк
6 KB
dan
Block on the WRITER lock when attempting to run recovery.
06 май 2020, 22:14
06 май 2020, 22:14
861fb1e
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/* ** 2010 February 1 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** This header file defines the interface to the write-ahead logging ** system. Refer to the comments below and the header comment attached to ** the implementation of each function in log.c for further details. */ #ifndef SQLITE_WAL_H #define SQLITE_WAL_H #include "sqliteInt.h" /* Macros for extracting appropriate sync flags for either transaction ** commits (WAL_SYNC_FLAGS(X)) or for checkpoint ops (CKPT_SYNC_FLAGS(X)): */ #define WAL_SYNC_FLAGS(X) ((X)&0x03) #define CKPT_SYNC_FLAGS(X) (((X)>>2)&0x03) #ifdef SQLITE_OMIT_WAL # define sqlite3WalOpen(x,y,z) 0 # define sqlite3WalLimit(x,y) # define sqlite3WalClose(v,w,x,y,z) 0 # define sqlite3WalBeginReadTransaction(y,z) 0 # define sqlite3WalEndReadTransaction(z) # define sqlite3WalDbsize(y) 0 # define sqlite3WalBeginWriteTransaction(y) 0 # define sqlite3WalEndWriteTransaction(x) 0 # define sqlite3WalUndo(x,y,z) 0 # define sqlite3WalSavepoint(y,z) # define sqlite3WalSavepointUndo(y,z) 0 # define sqlite3WalFrames(u,v,w,x,y,z) 0 # define sqlite3WalCheckpoint(q,r,s,t,u,v,w,x,y,z) 0 # define sqlite3WalCallback(z) 0 # define sqlite3WalExclusiveMode(y,z) 0 # define sqlite3WalHeapMemory(z) 0 # define sqlite3WalFramesize(z) 0 # define sqlite3WalFindFrame(x,y,z) 0 # define sqlite3WalFile(x) 0 #else #define WAL_SAVEPOINT_NDATA 4 /* Connection to a write-ahead log (WAL) file. ** There is one object of this type for each pager. */ typedef struct Wal Wal; /* Open and close a connection to a write-ahead log. */ int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**); int sqlite3WalClose(Wal *pWal, sqlite3*, int sync_flags, int, u8 *); /* Set the limiting size of a WAL file. */ void sqlite3WalLimit(Wal*, i64); /* Used by readers to open (lock) and close (unlock) a snapshot. A ** snapshot is like a read-transaction. It is the state of the database ** at an instant in time. sqlite3WalOpenSnapshot gets a read lock and ** preserves the current state even if the other threads or processes ** write to or checkpoint the WAL. sqlite3WalCloseSnapshot() closes the ** transaction and releases the lock. */ int sqlite3WalBeginReadTransaction(Wal *pWal, int *); void sqlite3WalEndReadTransaction(Wal *pWal); /* Read a page from the write-ahead log, if it is present. */ int sqlite3WalFindFrame(Wal *, Pgno, u32 *); int sqlite3WalReadFrame(Wal *, u32, int, u8 *); /* If the WAL is not empty, return the size of the database. */ Pgno sqlite3WalDbsize(Wal *pWal); /* Obtain or release the WRITER lock. */ int sqlite3WalBeginWriteTransaction(Wal *pWal); int sqlite3WalEndWriteTransaction(Wal *pWal); /* Undo any frames written (but not committed) to the log */ int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx); /* Return an integer that records the current (uncommitted) write ** position in the WAL */ void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData); /* Move the write position of the WAL back to iFrame. Called in ** response to a ROLLBACK TO command. */ int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData); /* Write a frame or frames to the log. */ int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int); /* Copy pages from the log to the database file */ int sqlite3WalCheckpoint( Wal *pWal, /* Write-ahead log connection */ sqlite3 *db, /* Check this handle's interrupt flag */ int eMode, /* One of PASSIVE, FULL and RESTART */ int (*xBusy)(void*), /* Function to call when busy */ void *pBusyArg, /* Context argument for xBusyHandler */ int sync_flags, /* Flags to sync db file with (or 0) */ int nBuf, /* Size of buffer nBuf */ u8 *zBuf, /* Temporary buffer to use */ int *pnLog, /* OUT: Number of frames in WAL */ int *pnCkpt /* OUT: Number of backfilled frames in WAL */ ); /* Return the value to pass to a sqlite3_wal_hook callback, the ** number of frames in the WAL at the point of the last commit since ** sqlite3WalCallback() was called. If no commits have occurred since ** the last call, then return 0. */ int sqlite3WalCallback(Wal *pWal); /* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released) ** by the pager layer on the database file. */ int sqlite3WalExclusiveMode(Wal *pWal, int op); /* Return true if the argument is non-NULL and the WAL module is using ** heap-memory for the wal-index. Otherwise, if the argument is NULL or the ** WAL module is using shared-memory, return false. */ int sqlite3WalHeapMemory(Wal *pWal); #ifdef SQLITE_ENABLE_SNAPSHOT int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot); void sqlite3WalSnapshotOpen(Wal *pWal, sqlite3_snapshot *pSnapshot); int sqlite3WalSnapshotRecover(Wal *pWal); int sqlite3WalSnapshotCheck(Wal *pWal, sqlite3_snapshot *pSnapshot); void sqlite3WalSnapshotUnlock(Wal *pWal); #endif #ifdef SQLITE_ENABLE_ZIPVFS /* If the WAL file is not empty, return the number of bytes of content ** stored in each frame (i.e. the db page-size when the WAL was created). */ int sqlite3WalFramesize(Wal *pWal); #endif /* Return the sqlite3_file object for the WAL file */ sqlite3_file *sqlite3WalFile(Wal *pWal); #ifdef SQLITE_ENABLE_SETLK_TIMEOUT int sqlite3WalWriteLock(Wal *pWal, int bLock); void sqlite3WalDb(Wal *pWal, sqlite3 *db); #endif #endif /* ifndef SQLITE_OMIT_WAL */ #endif /* SQLITE_WAL_H */