mysql慢查询操作实例分析【开启、测试、确认等】

本文实例讲述了mysql慢查询操作。分享给大家供大家参考，具体如下：

mysql有些sql会执行很慢，有可能造成服务器负载飙升

首先查询 确定影响负载的是mysql ，使用top命令，ps命令等

其次，进入MySQL，使用show full processlist查询执行中的sql语句，看看问题，使用explain 命令 查看状态

最后找出sql语句杀死或者优化

centos7上面安装mariadb服务

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1	yum -y install mariadb-server mariadb-devel

开启慢查询

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1	more /etc/my .cnf.d /server .cnf

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[mariadb] slow_query_log=ON slow_query_log_file= /usr/local/mysql/data/slow .log long_query_time=1

启动mariadb服务

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1	systemctl start mariadb

查询mysql的慢查询是否开启，以及多久的时间以上是慢查询

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MariaDB [(none)]> show variables like '%slow_query%' ; + ---------------------+--------------------------------+ | Variable_name    | Value             | + ---------------------+--------------------------------+ | slow_query_log   | ON               | | slow_query_log_file | /usr/ local /mysql/data/slow.log | + ---------------------+--------------------------------+ 2 rows in set (0.00 sec)   MariaDB [(none)]> show variables like 'long_query_time' ; + -----------------+----------+ | Variable_name  | Value  | + -----------------+----------+ | long_query_time | 1.000000 | + -----------------+----------+ 1 row in set (0.00 sec)

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#如果没用开启慢查询，可以在命令行开启 mysql> set global slow_query_log=1; Query OK, 0 rows affected (0.00 sec)

 测试慢查询，以及查看日志

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MariaDB [(none)]> select sleep(2); + ----------+ | sleep(2) | + ----------+ |    0 | + ----------+ 1 row in set (2.00 sec)

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[root@localhost ~] # more /usr/local/mysql/data/slow.log /usr/libexec/mysqld , Version: 5.5.60-MariaDB (MariaDB Server). started with: Tcp port: 0 Unix socket: /var/lib/mysql/mysql .sock Time         Id Command  Argument # Time: 180930 23:51:07 # User@Host: root[root] @ localhost [] # Thread_id: 2 Schema:  QC_hit: No # Query_time: 2.001017 Lock_time: 0.000000 Rows_sent: 1 Rows_examined: 0 SET timestamp=1538322667; select sleep (2);

 确认慢查询

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MariaDB [(none)]> show full processlist; #查看state慢查询在进行 + ----+------+-----------+------+---------+------+------------+-----------------------+----------+ | Id | User | Host   | db  | Command | Time | State   | Info         | Progress | + ----+------+-----------+------+---------+------+------------+-----------------------+----------+ | 3 | root | localhost | NULL | Query  |  9 | User sleep | select sleep(10)   |  0.000 | | 4 | root | localhost | NULL | Query  |  0 | NULL    | show full processlist |  0.000 | + ----+------+-----------+------+---------+------+------------+-----------------------+----------+ 2 rows in set (0.00 sec)   MariaDB [(none)]> show full processlist; #查看state慢查询已经结束，但是用户登陆了 + ----+------+-----------+------+---------+------+-------+-----------------------+----------+ | Id | User | Host   | db  | Command | Time | State | Info         | Progress | + ----+------+-----------+------+---------+------+-------+-----------------------+----------+ | 3 | root | localhost | NULL | Sleep  |  1 |    | NULL         |  0.000 | | 4 | root | localhost | NULL | Query  |  0 | NULL | show full processlist |  0.000 | + ----+------+-----------+------+---------+------+-------+-----------------------+----------+ 2 rows in set (0.00 sec)

希望本文所述对大家MySQL数据库计有所帮助。

原文链接：https://www.cnblogs.com/mmyy-blog/p/9732183.html