一、清除原因
因为之前打开了慢查询，导致此表越来越大达到47G，导致磁盘快被占满，使用xtrabackup进行备份的时候文件也超大。
mysql> show variables like 'log_output%';
Connection id: 1694401091
Current database: mysql
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output | TABLE |
+---------------+-------+
1 row in set (0.00 sec)
mysql> show variables like '%slow%';
+---------------------+-------------------------------------+
| Variable_name | Value |
+---------------------+-------------------------------------+
| log_slow_queries | ON |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | /home/mysql/data3311/sql01-slow.log |
+---------------------+-------------------------------------+
4 rows in set (0.00 sec)
