Percona MySQL查看没有访问的表
要找到实例里面某个表是否有访问，确实是比较难搞。
常用方法就是 开tcpdump或tshark持续抓包过滤怀疑的表名。
但是，如果我们用的是Percona分支的MySQL，这件事就变得简单多了。
Percona MySQL 下，我们可以打开userstat参数，通过查询系统统计表来获取用户、客户端和库表访问情况，注意：该功能只在MySQL的 Percona 发行版有效，社区版不带这个功能。
(none) > status--------------mysql Ver 14.14 Distrib 5.6.38-83.0, for Linux (x86_64) using 6.2Connection id:1222143Current database:Current user:root@localhostSSL:Not in useCurrent pager:stdoutUsing outfile:'/root/audit.log'Using delimiter:;Server version:5.6.38-83.0-log Percona Server (GPL), Release 83.0, Revision dc97471bd40Protocol version:10Connection:Localhost via UNIX socketServer characterset:utf8Db characterset:utf8Client characterset:utf8Conn. characterset:utf8UNIX socket:/tmp/mysql.sockUptime:110 days 8 hours 34 min 25 secThreads: 32 Questions: 1074250447 Slow queries: 1474 Opens: 136 Flush tables: 1 Open tables: 129 Queries per second avg: 112.665--------------(none) > use INFORMATION_SCHEMA(INFORMATION_SCHEMA) > show tables like '%_STATISTICS';+---------------------------------------------+| Tables_in_information_schema (%_STATISTICS) |+---------------------------------------------+| CLIENT_STATISTICS || INDEX_STATISTICS || TABLE_STATISTICS || THREAD_STATISTICS || USER_STATISTICS |+---------------------------------------------+5 rows in set (0.00 sec)set global userstat=ON;select * from INFORMATION_SCHEMA.CLIENT_STATISTICS;select * from INFORMATION_SCHEMA.INDEX_STATISTICS;select * from INFORMATION_SCHEMA.TABLE_STATISTICS;select * from INFORMATION_SCHEMA.THREAD_STATISTICS;select * from INFORMATION_SCHEMA.USER_STATISTICS;
如果要清理统计信息，可以使用下面的这几个命令：
FLUSH CLIENT_STATISTICS ;FLUSH INDEX_STATISTICS ;FLUSH TABLE_STATISTICS ;FLUSH THREAD_STATISTICS ;FLUSH USER_STATISTICS ;