1.18 MySQL慢查询日志

1. 是什么

将查询时间超过一定阙值的语句记录到日志中

show variables like '%slow_query_log%';

+---------------------+------------------------+
| Variable_name       | Value                  |
+---------------------+------------------------+
| slow_query_log      | OFF                    |
| slow_query_log_file | <example>-slow.log     |
+---------------------+------------------------+

show variables like '%long_query_time%';

+-----------------+-----------+
| Variable_name   | Value     |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+

2. 使用

2.1. 如何开启

set global slow_query_log=1;
set global long_query_time=3;

需要重新连接数据库才能看出效果

2.2. 如何查看

• 直接查看日志

tail -f /var/lib/mysql/<example>-slow.log -n 200

• 使用mysqldumpslow命令

3. 参考

https://mariadb.com/kb/en/library/documentation/mariadb-administration/server-monitoring-logs/slow-query-log/slow-query-log-overview/ https://dev.mysql.com/doc/refman/8.0/en/slow-query-log.html