How to use mysqlcheck when your MySQL table gets corrupted. Check & repair tables with MySQL’s mysqlcheck, a command line table maintenance program. Mysqlcheck checks, repairs, optimizes, or analyzes MySQL tables. In this post I’ll show you how to use
mysqlcheck to optimize all MySQL tables using a cronjob.
Mysqlcheck is ideal for automated optimizations of MySQL databases and tables.
mysqlcheck in an automated and unattended task, we use a cronjob to optimize all MySQL databases on a daily or weekly basis. The
mysqlcheck utility optimizes tables and databases, which means that fragmented tables are defragmented.
Create an unprivileged MySQL user
The first step is to create an unprivileged MySQL user, so log on to your mysql console (in my case, my maintenance user also needs reload as privilege):
mysql -u root -p
Create the MySQL maintenance user and grant required privileges:
mysql> create user 'maintenance'@'localhost'; mysql> grant select, insert, reload on *.* to 'maintenance'@'localhost';
And flush all privileges to make it effective:
mysql> flush privileges; Query OK, 0 rows affected (0.15 sec)
Cronjob for MySQL maintenance
The cron software utility is a time-based job scheduler in Unix-like computer operating systems. We use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.
In order to run the maintenance unattended and automated, we create a cronjob for it (in one line):
echo "0 4 * * Sun root mysqlcheck -u maintenance --optimize --all-databases" > /etc/cron.d/mysqlcheck
This cron runs every Sunday morning at 04:00 AM. The systems root user starts mysqlcheck under MySQL’s user ‘maintenance’.
That’s all basicly. Because
mysqlcheck locks each table, and therefore unavailable to other sessions while it is being processed, you must not schedule this task on busy working day hours. Even for check operations, the table is locked with a READ lock only.
Table maintenance operations can be time-consuming, particularly for large tables. If you use the
--all-databases option to process all tables in one or more databases, an invocation of mysqlcheck might take a long time.
Note: Mysqlcheck options:
MariaDB 5.5 doesn’t like multiple contradicting commands as mysqlcheck parameters, so something like the following would fail with an error:
--auto-repair --check --optimize --all-databases