9.2 Historique de modification

When started with the --log-update=file_name option, mysqld writes a log file containing all SQL commands that update data. The file is written in the data directory and has a name of file_name.#, where # is a number that is incremented each time you execute mysqladmin refresh or mysqladmin flush-logs, the FLUSH LOGS statement, or restart the server.

If you use the --log or -l options, the filename is `hostname.log', and restarts and refreshes do not cause a new log file to be generated. By default, the mysql.server script starts the MySQL server with the -l option. If you need better performance when you start using MySQL in a production environment, you can remove the -l option from mysql.server.

Update logging is smart since it logs only statements that really update data. So an UPDATE or a DELETE with a WHERE that finds no rows is not written to the log. It even skips UPDATE statements that set a column to the value it already has.

If you want to update a database from update log files, you could do the following (assuming your log files have names of the form `file_name.#'):

shell> ls -1 -t -r file_name.[0-9]* | xargs cat | mysql

ls is used to get all the log files in the right order.

This can be useful if you have to revert to backup files after a crash and you want to redo the updates that occurred between the time of the backup and the crash.

You can also use the update logs when you have a mirrored database on another host and you want to replicate the changes that have been made to the master database.