Slow Query Log Extended Statistics

Overview

• Added extra logging to slow log of 'Thread_id, Schema, Query Cache hit, Rows sent and Rows examined'

• Added optional logging to slow log, through log_slow_verbosity, of query plan statistics

• Added new session variables log_slow_rate_limit, log_slow_verbosity, log_slow_filter

• Added log-slow-file as synonym for 'slow-log-file', as most slow-log variables start with 'log-slow'

• Added log-slow-time as synonym for long-query-time.

Session Variables

log_slow_verbosity

You can set the verbosity of what's logged to the slow query log by setting the variable to a combination of the following values:

• All (From )

  • Enable all verbosity options.

• Query_plan

• Warnings (From )

  • Print all errors, warnings and notes related to statement, up to log_slow_max_warnings lines.

• full.

The default value for log_slow_verbosity is ' ', to be compatible with MySQL 5.1.

The possible values for log_slow_verbosity areinnodb,query_plan,explain,engine,warnings. Multiple options are separated by ','. log_slow_verbosity is not supported when log_output='TABLE'.

In the future we will add more engine statistics and also support for other engines.

log_slow_filter

You can define which queries to log to the slow query log by setting the variable to a combination of the following values:

• All (From )

  • Enable all filter options. log_slow_filter will be shown as having all options set.

• admin

Multiple options are separated by ','. If you don't specify any options everything will be logged (same as setting the value to All.

log_slow_rate_limit

The variable limits logging to the slow query log by not logging every query (only one query / log_slow_rate_limit is logged). This is mostly useful when debugging and you get too much information to the slow query log.

Note that in any case, only queries that takes longer than log_slow_time orlong_query_time' are logged (as before).

log_slow_max_warnings

MariaDB starting with

If one enables the warning option for log_slow_verbosity, all notes and warnings for a slow query will also be added to the slow query log. This is very usable when one has enabled warnings for . log_slow_max_warnings limits the number of warnings printed to the slow query log per query. The default value is 10.

Credits

Part of this addition is based on the patch from .

See also

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