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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 ) ?

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5 Answers 5

up vote 11 down vote accepted

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

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1  
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 '11 at 22:01
2  
Note that log-slow-queries is deprecated as of 5.1.29. The one to use thereafter is slow-query-log. –  Riedsio Jan 13 '11 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 '11 at 22:25

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

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

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Can you link to the manual for a short answer like this? –  Brian Ballsun-Stanton Jan 12 '11 at 1:59

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.

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

At your shell:

grep slow /etc/my.cnf
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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.

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