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I'm looking at the slow query log from a drupal-based webapp, and have lines that look like this:
# Query_time: 3257 Lock_time: 0 Rows_sent: 272 Rows_examined: 272
# Query_time: 1654 Lock_time: 0 Rows_sent: 222 Rows_examined: 222
# Query_time: 3292 Lock_time: 0 Rows_sent: 269 Rows_examined: 269
# Query_time: 1029 Lock_time: 0 Rows_sent: 172 Rows_examined: 172
# Query_time: 2126 Lock_time: 0 Rows_sent: 251 Rows_examined: 251
# Query_time: 1731 Lock_time: 0 Rows_sent: 229 Rows_examined: 229
Are these times indicating that the associated queries took between 1 and 3+ seconds (slow but not terrible) to execute, or between 1,000 and 3,000+ seconds (completely unacceptable)? I understand that the long_query_time option is specified in seconds, but do the log messages follow this same convention, or do they use milliseconds instead?
Edit: this is with MySQL version 5.0.45.
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The slow query log consists of SQL statements that take more than long_query_time seconds to execute and require at least min_examined_row_limit rows to be examined. The slow query log can be used to find queries that take a long time to execute and are therefore candidates for optimization.
To make reading the log contents easier, you can use the mysqldumpslow command-line utility to process a slow query log file and summarize its contents: ~ $ mysqldumpslow -a /var/lib/mysql/slowquery. log Reading mysql slow query log from /var/lib/mysql/slowquery.
By default, when the slow query log is enabled, it logs any query that takes longer than 10 seconds to run. To change this interval, type the following command, replacing X with the time in seconds: Copy SET GLOBAL long_query_time = X; By default, the slow query log file is located at /var/lib/mysql/hostname-slow. log.
It's in seconds. The 'resolution of microseconds' means, that you can have up to microsecond precision after a decimal (although AFAIK it need a patch to actually write with such precision)
https://github.com/wvanbergen/request-log-analyzer/wiki/MySQL-slow-query-log
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Only since MySQL 5.1.21 that you can specify a decimal value and has a resolution of microsecond. http://dev.mysql.com/doc/refman/5.1/en/slow-query-log.html
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