Makefile學習之路(3) — Makefile的函式
阿新 • • 發佈:2020-12-28
MySQL 慢查詢日誌
簡介
MySQL 慢查詢日誌是排查問題 SQL 語句,以及檢查當前 MySQL 效能的一個重要功能。
- 檢視是否開啟慢查詢功能:
mysql> show variables like 'slow_query%'; +---------------------+------------------------------------+ | Variable_name | Value | +---------------------+------------------------------------+ | slow_query_log | OFF | | slow_query_log_file | /var/lib/mysql/instance-1-slow.log | +---------------------+------------------------------------+ 2 rows in set (0.01 sec)
mysql> show variables like 'long_query_time';
+-----------------+-----------+
| Variable_name | Value |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+
1 row in set (0.00 sec)
說明:
slow_query_log 慢查詢開啟狀態
slow_query_log_file 慢查詢日誌存放的位置(這個目錄需要MySQL的執行帳號的可寫許可權,一般設定為MySQL的資料存放目錄)
配置
臨時配置
預設沒有開啟慢查詢日誌記錄,通過命令臨時開啟:
mysql> set global slow_query_log='ON'; Query OK, 0 rows affected (0.00 sec) mysql> set global slow_query_log_file='/var/lib/mysql/instance-1-slow.log'; Query OK, 0 rows affected (0.00 sec) mysql> set global long_query_time=2; Query OK, 0 rows affected (0.00 sec)
永久配置
修改配置檔案達到永久配置狀態:
/etc/mysql/conf.d/mysql.cnf
[mysqld]
slow_query_log = ON
slow_query_log_file = /var/lib/mysql/instance-1-slow.log
long_query_time = 2
配置好後,重新啟動 MySQL 即可。
測試
通過執行下面的命令,達到問題 SQL 語句的執行:
mysql> select sleep(2);
+----------+
| sleep(2) |
+----------+
| 0 |
+----------+
1 row in set (2.00 sec)
然後檢視慢查詢日誌內容:
$ cat /var/lib/mysql/instance-1-slow.log
/usr/sbin/mysqld, Version: 8.0.13 (MySQL Community Server - GPL). started with:
Tcp port: 3306 Unix socket: /var/run/mysqld/mysqld.sock
Time Id Command Argument
/usr/sbin/mysqld, Version: 8.0.13 (MySQL Community Server - GPL). started with:
Tcp port: 3306 Unix socket: /var/run/mysqld/mysqld.sock
Time Id Command Argument
# Time: 2018-12-18T05:55:15.941477Z
# User@Host: root[root] @ localhost [] Id: 53
# Query_time: 2.000479 Lock_time: 0.000000 Rows_sent: 1 Rows_examined: 0
SET timestamp=1545112515;
select sleep(2);