MySQL查询日志介绍

MySQL查询日志介绍

　　MySQL的查询日志记录了所有MySQL数据库请求的信息。无论这些请求是否得到了正确的执行。默认文件名为hostname.log。默认情况下MySQL查询日志是关闭的。生产环境，如果开启MySQL查询日志，对性能还是有蛮大的影响的。另外很多时候，MySQL慢查询日志基本可以定位那些出现性能问题的SQL，所以MySQL查询日志应用的场景其实不多，有点鸡肋的感觉，它跟SQL Server中的profiler有点类似，但是这个不能跟踪某个会话、用户、客户端。它只能对整个数据库进行跟踪。MySQL查询日志本身比较简单，网上介绍的不多，官方资料也就那么短短一篇。

MySQL查询日志配置

　　MySQL中的参数general_log用来控制开启、关闭MySQL查询日志,参数general_log_file用来控制查询日志的位置。所以如果你要判断MySQL数据库是否开启了查询日志，可以使用下面命令。general_log为ON表示开启查询日志，OFF表示关闭查询日志。

mysql> show variables like '%general_log%';
+------------------+------------------------------+
| Variable_name    | Value                        |
+------------------+------------------------------+
| general_log      | OFF                          |
| general_log_file | /var/lib/mysql/DB-Server.log |
+------------------+------------------------------+
2 rows in set (0.00 sec)

mysql> 

另外，MySQL的查询日志支持写入文件或写入数据表两种形式，这个由参数log_output控制，如下所示：

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

mysql> 

这三个参数general_log、 general_log_file、 log_output都是动态参数，可以随时动态修改。

1、开启MySQL查询日志

mysql> set global general_log = on;
Query OK, 0 rows affected (0.11 sec)

mysql> show variables like 'general_log';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| general_log   | ON    |
+---------------+-------+
1 row in set (0.02 sec)

mysql> 

2、关闭MySQL查询日志

mysql> show variables like 'general_log';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| general_log   | ON    |
+---------------+-------+
1 row in set (0.01 sec)

mysql> set global general_log=off;
Query OK, 0 rows affected (0.01 sec)

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

mysql> 

3、设置日志输出方式为表（如果设置log_output=table的话，则日志结果会记录到名为gengera_log的表中，这表的默认引擎是CSV）：

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

mysql> set global log_output='table';
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'log_output';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output    | TABLE |
+---------------+-------+
1 row in set (0.01 sec)

mysql> 

查看查询日志信息。

mysql> select * from mysql.general_log;
+---------------------+---------------------------+-----------+-----------+--------------+----------------------------------+
| event_time          | user_host                 | thread_id | server_id | command_type | argument                         |
+---------------------+---------------------------+-----------+-----------+--------------+----------------------------------+
| 2017-07-06 12:32:05 | root[root] @ localhost [] |         1 |         1 | Query        | show variables like 'general%'   |
| 2017-07-06 12:32:28 | root[root] @ localhost [] |         1 |         1 | Query        | show variables like 'log_output' |
| 2017-07-06 12:32:41 | root[root] @ localhost [] |         1 |         1 | Query        | select * from MyDB.test          |
| 2017-07-06 12:34:36 | [root] @ localhost []     |         3 |         1 | Connect      | root@localhost on                |
| 2017-07-06 12:34:36 | root[root] @ localhost [] |         3 |         1 | Query        | KILL QUERY 1                     |
| 2017-07-06 12:34:36 | root[root] @ localhost [] |         3 |         1 | Quit         |                                  |
| 2017-07-06 12:34:51 | root[root] @ localhost [] |         1 |         1 | Query        | select * from mysql.general_log  |
+---------------------+---------------------------+-----------+-----------+--------------+----------------------------------+
7 rows in set (0.02 sec)

mysql> 

4： 查询日志归档

mysql> system mv /var/lib/mysql/DB-Server.log  /var/lib/mysql/DB-Server.log.20170706

mysql> system mysqladmin flush-logs -p

Enter password:

或者你在shell中执行下面命令

[root@DB-Server mysql]# mv /var/lib/mysql/DB-Server.log  /var/lib/mysql/DB-Server.log.20170706

[root@DB-Server mysql]# mysqladmin flush-logs -p

Enter password:

5： 修改查询日志名称或位置

mysql> show variables like 'general_log%';
+------------------+------------------------------+
| Variable_name    | Value                        |
+------------------+------------------------------+
| general_log      | ON                           |
| general_log_file | /var/lib/mysql/DB-Server.log |
+------------------+------------------------------+
2 rows in set (0.00 sec)

mysql> set global general_log='OFF';
Query OK, 0 rows affected (0.00 sec)

mysql> set global general_log_file='/u02/mysql_log.log';
Query OK, 0 rows affected (0.00 sec)
mysql> set global general_log='ON';
Query OK, 0 rows affected (0.02 sec)

转载:https://www.cnblogs.com/kerrycode/p/7130403.html