1.Dd December 19, 2018 2.Dt SQLITE3_WAL_HOOK 3 3.Os 4.Sh NAME 5.Nm sqlite3_wal_hook 6.Nd Write-Ahead Log Commit Hook 7.Sh SYNOPSIS 8.Ft void * 9.Fo sqlite3_wal_hook 10.Fa "sqlite3*" 11.Fa "int(*)(void *,sqlite3*,const char*,int)" 12.Fa "void* " 13.Fc 14.Sh DESCRIPTION 15The sqlite3_wal_hook() function is used to register 16a callback that is invoked each time data is committed to a database 17in wal mode. 18.Pp 19The callback is invoked by SQLite after the commit has taken place 20and the associated write-lock on the database released , so the implementation 21may read, write or checkpoint the database as required. 22.Pp 23The first parameter passed to the callback function when it is invoked 24is a copy of the third parameter passed to sqlite3_wal_hook() when 25registering the callback. 26The second is a copy of the database handle. 27The third parameter is the name of the database that was written to 28- either "main" or the name of an ATTACH-ed database. 29The fourth parameter is the number of pages currently in the write-ahead 30log file, including those that were just committed. 31.Pp 32The callback function should normally return SQLITE_OK. 33If an error code is returned, that error will propagate back up through 34the SQLite code base to cause the statement that provoked the callback 35to report an error, though the commit will have still occurred. 36If the callback returns SQLITE_ROW or SQLITE_DONE, 37or if it returns a value that does not correspond to any valid SQLite 38error code, the results are undefined. 39.Pp 40A single database handle may have at most a single write-ahead log 41callback registered at one time. 42Calling sqlite3_wal_hook() replaces any previously 43registered write-ahead log callback. 44Note that the sqlite3_wal_autocheckpoint() 45interface and the wal_autocheckpoint pragma 46both invoke sqlite3_wal_hook() and will overwrite 47any prior sqlite3_wal_hook() settings. 48.Sh SEE ALSO 49.Xr sqlite3_wal_autocheckpoint 3 , 50.Xr sqlite3_wal_hook 3 , 51.Xr SQLITE_OK 3 52