31

Just as the title says, where can I see it ?

Are there any config options for it ( like how many ms would determine if a query is slow or not ) ?

5 Answers 5

23

You can find it in the default directory, depending on your install. For instance, on my Red Hat, it's /var/log/mysql/

Query time is time, in seconds, over which it should start recording. This can be done at startup and at runtime.

log-slow-queries = /var/log/mysql/mysql-slow.log

long_query_time = 1

3
  • 5
    At my site, I discovered someone has set log_slow_queries=ON. So I have a file in my datadir called ON containing the log. That was confusing...
    – Gaius
    Jan 3, 2011 at 22:01
  • 6
    Note that log-slow-queries is deprecated as of 5.1.29. The one to use thereafter is slow-query-log.
    – Riedsio
    Jan 13, 2011 at 22:19
  • 1
    Also note that beginning with MySQL 5.1.21, a resolution of microseconds is supported when logging to a file.
    – Riedsio
    Jan 13, 2011 at 22:25
29

In MySQL : show global variables like '%slow%';

Update : here's a link to the manual: link text

1
  • 1
    Can you link to the manual for a short answer like this? Jan 12, 2011 at 1:59
7

These are the pertinent options (and settings) I generally have/use in all my my.cnfs to log slow queries:

log_output=FILE
slow_query_log=1
slow_query_log_file=/var/log/mysql/mysql.slow 
long_query_time=0.001 
log-queries-not-using-indexes=0

Note that for long_query_time,

Beginning with MySQL 5.1.21 ... a resolution of microseconds is supported when logging to a file.

3

Search your mysqld config file (usually, /etc/my.cnf)

At your shell:

grep slow /etc/my.cnf
3

Here is something to consider as well :

If you use the option

log-output=TABLE

in you /etc/my.cnf file, look for the slow log to be a CSV storage engine based table located in, of all places, the mysql schema.

This affects the general log as well, once you enable it.

2
  • Can you log slow queries to table but the "normal" log into a file?
    – surfmuggle
    Nov 11, 2020 at 20:31
  • @surfmuggle Yes you can. If you put log-output=FILE,TABLE. that would do it !!! You must restart mysql to implement this. Nov 11, 2020 at 21:23

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