解决MySQL 5.6版的Function ‘innodb’ already exists错误

MySQL 5.6启动后，其日志文件存在如下错误：

......
2015-10-28 13:27:05 25054 [ERROR] Function 'innodb' already exists
2015-10-28 13:27:05 25054 [Warning] Couldn't load plugin named 'innodb' with soname 'ha_innodb.so'.
2015-10-28 13:27:05 25054 [ERROR] Function 'federated' already exists
2015-10-28 13:27:05 25054 [Warning] Couldn't load plugin named 'federated' with soname 'ha_federated.so'.
2015-10-28 13:27:05 25054 [ERROR] Function 'blackhole' already exists
2015-10-28 13:27:05 25054 [Warning] Couldn't load plugin named 'blackhole' with soname 'ha_blackhole.so'.
2015-10-28 13:27:05 25054 [ERROR] Function 'archive' already exists
2015-10-28 13:27:05 25054 [Warning] Couldn't load plugin named 'archive' with soname 'ha_archive.so'.
...... 

分析原因，是MySQL 5.6没有以下四个插件所致。

MySQL 5.6服务器初始化脚本添加了以下的插件表，而实际上MySQL 5.6不依赖于任何插件。

mysql> select * from mysql.plugin;
+-----------+-----------------+
| name      | dl              |
+-----------+-----------------+
| innodb    | ha_innodb.so    |
| federated | ha_federated.so |
| blackhole | ha_blackhole.so |
| archive   | ha_archive.so   |
+-----------+-----------------+
4 rows in set (0.00 sec) 

解决它很简单，执行命令：

mysql> delete from mysql.plugin;
Query OK, 4 rows affected (0.00 sec) 

删掉这4个插件，清除日志，重启MySQL服务，可以看到，MySQL无错运行。