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(mysql.info)Update log

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The Update Log
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*NOTE*: The update log is replaced by the binary log. Note: Binary
log.  With this you can do anything that you can do with the update
log.

When started with the `--log-update[=file_name]' option, `mysqld'
writes a log file containing all SQL commands that update data. If no
filename is given, it defaults to the name of the host machine. If a
filename is given, but it doesn't contain a path, the file is written
in the data directory. If `file_name' doesn't have an extension,
`mysqld' will create log file names like so: `file_name.###', where
`###' is a number that is incremented each time you execute `mysqladmin
refresh', execute `mysqladmin flush-logs', execute the `FLUSH LOGS'
statement, or restart the server.

*NOTE:* For the above scheme to work, you should NOT create your own
files with the same filename as the update log + some extensions that
may be regarded as a number, in the directory used by the update log!

If you use the `--log' or `-l' options, `mysqld' writes a general log
with a filename of `hostname.log', and restarts and refreshes do not
cause a new log file to be generated (although it is closed and
reopened). In this case you can copy it (on Unix) by doing:

     mv hostname.log hostname-old.log
     mysqladmin flush-logs
     cp hostname-old.log to-backup-directory
     rm hostname-old.log

Update logging is smart because 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.

The update logging is done immediately after a query completes but
before any locks are released or any commit is done. This ensures that
the log will be logged in the execution order.

If you want to update a database from update log files, you could do the
following (assuming your update logs 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.