MySQL查詢日志介紹

MySQL查詢日志介紹

　　MySQL的查詢日志記錄了所有MySQL數據庫請求的信息。無論這些請求是否得到了正確的執行。默認文件名為hostname.log。默認情況下MySQL查詢日志是關閉的。生產環境，如果開啟MySQL查詢日志，對性能還是有蠻大的影響的。另外很多時候，MySQL慢查詢日志基本可以定位那些出現性能問題的SQL，所以MySQL查詢日志應用的場景其實不多，有點雞肋的感覺，它跟SQL Server中的profiler有點類似，但是這個不能跟蹤某個會話、用戶、客戶端。它只能對整個數據庫進行跟蹤。MySQL查詢日志本身比較簡單，網上介紹的不多，官方資料也就那么短短一篇。

 

MySQL查詢日志配置

　　MySQL中的參數general_log用來控制開啟、關閉MySQL查詢日志,參數general_log_file用來控制查詢日志的位置。所以如果你要判斷MySQL數據庫是否開啟了查詢日志，可以使用下面命令。general_log為ON表示開啟查詢日志，OFF表示關閉查詢日志。

 

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的查詢日志支持寫入文件或寫入數據表兩種形式，這個由參數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> 

 

這三個參數general_log、 general_log_file、 log_output都是動態參數，可以隨時動態修改。

 

1、開啟MySQL查詢日志

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、關閉MySQL查詢日志

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、設置日志輸出方式為表（如果設置log_output=table的話，則日志結果會記錄到名為gengera_log的表中，這表的默認引擎是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> 

 

查看查詢日志信息。

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： 查詢日志歸檔

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中執行下面命令

 

[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： 修改查詢日志名稱或位置

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)

 

 

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