通常服務沒問題，慢查詢檔案大小只會越來越大，到一段時間需要清理
以下是正常開啟時的設置
＃查看慢查詢日志相關內容
MySQL [(none)]> show variables like '%slow%';
+---------------------------+----------------------------+
| Variable_name | Value |
+---------------------------+----------------------------+
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | /data/mysql/mysql-slow.log |
+---------------------------+----------------------------+
5 rows in set (0.00 sec)
＃查看執行超過多久會被寫入慢查詢日志中
MySQL [(none)]> show variables like '%long_query_time%';
+-----------------+----------+
| Variable_name | Value |
+-----------------+----------+
| long_query_time | 1.000000 |
+-----------------+----------+
1 row in set (0.00 sec)
當檔案過大時，需要切換時
#先關閉OFF
MySQL [(none)]> set global slow_query_log=0;
Query OK, 0 rows affected (0.01 sec)
關閉slow_log後，再進MYSQL資料夾裡面更名
cd /data/mysql/
mv mysql-slow.log mysql-slow.log.20190814old
再次進入MYSQL
＃重新下路徑（避免設定跑掉，或者下之前也可以先 show variables like '%slow%'; 查看）
MySQL [(none)]> set global slow_query_log_file='/data/mysql/mysql-slow.log';
Query OK, 0 rows affected (0.00 sec)
#重新開啟slow_log為ON
MySQL [(none)]> set global slow_query_log=1;
Query OK, 0 rows affected (0.11 sec)
#查詢是否已啟動
MySQL [(none)]> show variables like '%slow%';
+---------------------------+----------------------------+
| Variable_name | Value |
+---------------------------+----------------------------+
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | /data/mysql/mysql-slow.log |
+---------------------------+----------------------------+
5 rows in set (0.00 sec)
啟動後可進入MYSQL資料夾內查看是否有新的檔案產生，檔案是否有慢慢增大～有就成功了
接著壓縮檔案 tar -czf mysql-slow.log.
20190814
old.tar.gz mysql-slow.log.
20190814old 做為留抵用
