I recently tried to run
INSERT INTO general_log SELECT * FROM mysql.general_log;
but that failed a few hours in because I ran out of disk space.
'SELECT COUNT(*) FROM general_log' returns 0, yet ibdata1 is still
49GB (started at 3GB before the INSERT; the source mysql.general_log,
a CSV table,
Your innodb data file just auto-extended until you either reached its max or
ran out of disk space if you had no max.
The only way I know to reduce it is to dump all the innodb tables, drop the
innodb data file and logs (and drop the innodb tables if you're using
file-per-table), restart mysql,
