MySQL General Log

The MySQL general log records every statement and connection event that reaches the server. It is one of the fastest ways to figure out what a client is actually sending when something looks off, and it takes only a few commands to get running.

Enabling the General Log

By default the general log is off. To turn it on for the current session and persist the setting, run:

SET GLOBAL general_log = 'OFF';
ALTER TABLE mysql.general_log ENGINE = MyISAM;
SET GLOBAL general_log = 'ON';

The ALTER TABLE step ensures the mysql.general_log table uses the MyISAM engine, which supports concurrent reads while the log is being written. Without that, you may hit lock contention when querying the table.

Querying the Log

Once the log is active, you can inspect recent entries directly:

SELECT * FROM mysql.general_log LIMIT 2;

Each row contains the event timestamp, the connection ID, the command type (Query, Connect, Quit, etc.), and the full statement text.

Practical Tips

• Scope it down. The general log can grow quickly on a busy server. Use LIMIT and filter by event_time or thread_id to keep queries fast.
• Turn it off when done. Run SET GLOBAL general_log = 'OFF'; once you have the data you need so you are not writing every statement to disk indefinitely.
• Check the file log too. If you prefer file-based logging, set general_log_file to a path under your data directory and confirm log_output includes FILE.

Disabling the General Log

When you are finished troubleshooting, disable it to stop the disk I/O overhead:

SET GLOBAL general_log = 'OFF';

If you want the change to survive a restart, also update the configuration file (my.cnf or my.ini) and set general_log = 0 under the [mysqld] section.

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