How to Enable the Slow Query Log in MySQL® or MariaDB
Last modified: October 22, 2020
Enabling the Slow Query Log for MySQL® or MariaDB can be a useful tool to diagnose performance and efficiency issues affecting your server. By identifying queries that are particularly slow in their execution, you can address them by restructuring the application that triggers your queries. You can also rebuild the queries themselves to ensure that they are constructed as efficiently as possible.
For more information about the MySQL slow query log, read the MySQL 5.7 Reference Manual: The Slow Query Log documentation.
Enable the Slow Query Log
To enable the Slow Query Log for MySQL or MariaDB:
Log in to your server as the
rootuser via SSH.
my.cnffile with a text editor and add the following block of code under the
slow_query_log = 1 slow-query_log_file = /var/log/mysql-slow.log long_query_time = 2Note:
In MySQL 5.6 and older, use the
log-slow-queriesvariable instead of the
/var/log/mysql-slow.logfile and set its user as the
mysqluser. To do this, run the following commands:
touch /var/log/mysql-slow.log chown mysql:mysql /var/log/mysql-slow.log
Restart MySQL or MariaDB. To do this, run the following command:
Start monitoring the slow query logfile. To analyze and print the file’s summary, run the
mysqldumpslowcommand. For example, to print all slow queries that the system previously recorded, run the following command:
mysqldumpslow -a /var/log/mysql-slow.log
For a complete list of options to use with the
mysqldumpslow command, read MySQL’s mysqldumpslow article.