Find out slow sql of mysql_find slow sql-优快云博客

本文介绍了如何通过开启MySQL慢查询日志来定位并优化慢查询。包括设置慢启动时间、查看慢查询配置及日志文件路径等关键步骤。

Recent days, I should do a sql tuning for a mysql database, and I know a bit of mysql db. In order to find the slow sql, i do the slow_query_log on to collect the slow sql.

mysql> show variables like 'slow%';
+---------------------+-------------------------------------------+
| Variable_name       | Value                                     |
+---------------------+-------------------------------------------+
| slow_launch_time    | 2                                         |
| slow_query_log      | ON                                        |
| slow_query_log_file | /opt/mysql_data/mysql/mysql-test-slow.log |
+---------------------+-------------------------------------------+
3 rows in set (0.00 sec)

mysql> set global slow_launch_time=5;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'slow%';
+---------------------+-------------------------------------------+
| Variable_name       | Value                                     |
+---------------------+-------------------------------------------+
| slow_launch_time    | 5                                         |
| slow_query_log      | ON                                        |
| slow_query_log_file | /opt/mysql_data/mysql/mysql-test-slow.log |
+---------------------+-------------------------------------------+
3 rows in set (0.00 sec)

We can read /opt/mysql_data/mysql/mysql-test-slow.log to find slow sql.