MySQL之慢查询日志分析

Posted 2021-02-04 峰哥ge

在mysql命令行中查看慢查询日志是否打开了：

mysql> show variables like \'%slow_query%\';
+---------------------------+-------------------------------------------+
| Variable_name             | Value                                     |
+---------------------------+-------------------------------------------+
| slow_query_log            | OFF                                       |
| slow_query_log_file       | /data/data_mysql/ip-172-31-22-29-slow.log |
+---------------------------+-------------------------------------------+

从上面可以看出没有打开慢查询日志的功能，现在我们打开一下，修改配置文件即可，修改后重启服务器。慢查询还有一个值比较重要，就是知道慢查询的时间：

mysql> show variables like \'long_query_time\';
+-----------------+----------+
| Variable_name   | Value    |
+-----------------+----------+
| long_query_time | 6.000000 |
+-----------------+----------+
1 row in set (0.00 sec)

现在修改为两秒：

mysql> set long_query_time=2;
Query OK, 0 rows affected (0.00 sec)

现在我们执行一个超过2秒的命令，看看效果：

mysql> select * from sbtest1 group by k order by c desc  limit 1 ;
+--------+--------+-------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------+
| id     | k      | c                                                                                                                       | pad                                                         |
+--------+--------+-------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------+
| 453457 | 405843 | 99999937916-36259215105-74975791934-92968503070-23401591942-58585485414-51662851642-34478065889-45334022082-96106417569 | 77221010299-62957510796-01772448764-69834738016-84613386231 |
+--------+--------+-------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------+
1 row in set (2.18 sec)

现在我们查看一下慢查询日志；