mysql_slow_query []

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Slow Query Logs

You can check to see if slow query logging is currently enabled. The following command assumes you have configured .my.cnf file:

show full variables like "%slow%";

Or you can run the following from the command line:

mysql -e 'show variables;' | grep slow_query_log

Output should show something similar to:

+---------------------+---------------------------------+
| Variable_name       | Value                           |
+---------------------+---------------------------------+
| log_slow_queries    | OFF                             |
| slow_launch_time    | 2                               |
| slow_query_log      | OFF                             |
| slow_query_log_file | /var/run/mysqld/mysqld-slow.log |
+---------------------+---------------------------------+

Or:

slow_query_log  OFF
slow_query_log_file     /var/run/mysqld/mysqld-slow.log

How many slow queries?

You can also use the following command to view if you currently have any slow queries (if logging has been enabled):

show status like '%slow%';
<sxh>
Or from the command line:
<sxh bash>
mysql -e 'show status;' | grep -i slow

This should produce a similar output:

Slow_launch_threads     0
Slow_queries    0

There are now 2 options for configuring slow query logging. You can add the settings in the .my.cnf file or you can set the variables through the mysql command line.

Option 1

If run the following command it will set slow query logging without needing to restart mysql

mysql -e 'set global log_slow_queries = 1;'

You can now run the following command and it should produce an output saying that slow_query logging is enabled:

mysql -e 'show variables;' | grep slow

Option 2 - .my.cnf

slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow.log
long_query_time = 10
log_queries_not_using_indexes = 1

Change permissions so that mysqld can write to the specified log file. Giving write permissions to the 'other' group should suffice.