环境说明：

MySQL5.6.40 上xtrabackup全备备份的数据导入到mysql5.7.24实例上，启动MySQL5.7的服务，登录数据库MySQL5.7实例。但是在drop user

[email protected]‘127.0.0.1‘时，报错如下：

2019-08-15T19:02:31.160910+08:00 1546 [ERROR] /usr/local/mysql5.7/bin/mysqld: Column count of mysql.user is wrong. Expected 45, found 43. Created with MySQL 50640, now running 50724. Please use mysql_upgrade to fix this error.

mysql实例版本如下：

[[email protected] ~]# /usr/local/mysql/bin/mysqld -V

/usr/local/mysql/bin/mysqld Ver 5.6.40 for Linux on x86_64 (Source distribution)

[[email protected] ~]# /usr/local/mysql5.7/bin/mysqld -V

/usr/local/mysql5.7/bin/mysqld Ver 5.7.24 for linux-glibc2.12 on x86_64 (MySQL Community Server (GPL))

解决办法：升级下MySQL5.7

/usr/local/mysql5.7/bin/mysql_upgrade -uroot -p‘ln.orge#dieurw5199‘ -S /tmp/3306.sock

Checking if update is needed.

Checking server version.

Running queries to upgrade MySQL server.

Checking system database.

testdb29.dtr_wx_gotourl OK

testdb29.dtr_zone OK

testdb29.hm_planstats_h OK

Upgrade process completed successfully.

Checking if update is needed.

登录MySQL5.7删除库的用户，删除成功

mysql> drop user [email protected]‘127.0.0.1‘;

Query OK, 0 rows affected (0.00 sec)

提示：此时的mysql5.7.24实例并没有重启

此刻创建一个定时器调用存储过程时，报错如下：

mysql> CREATE EVENT test1

-> ON SCHEDULE EVERY 2 second STARTS TIMESTAMP ‘2019-08-10 16:16:22‘

-> ON COMPLETION PRESERVE

-> DO

-> BEGIN

-> CALL test1();

-> END//

ERROR 1577 (HY000): Cannot proceed because system tables used by Event Scheduler were found damaged at server start

mysql> show events;

ERROR 1577 (HY000): Cannot proceed because system tables used by Event Scheduler were found damaged at server start

###提示无法继续，因为在服务器启动时发现事件调度程序使用的系统表已损坏

此刻查看mysql 系统变量报错如下：

mysql> show variables like ‘event_scheduler‘;

ERROR 1682 (HY000): Native table ‘performance_schema‘.‘session_variables‘ has the wrong structure

出现的原因是我升级了mysql的版本，但是没有重启mysql实例

需要重启MySQL5.7.24服务。否则会导致MySQL的部分系统表识别不到。

service restart mysql5.7.24

到此处问题解决了

mysql> show events;

Empty set (0.00 sec)

mysql> show variables like ‘event_scheduler‘;

+-----------------+-------+

| Variable_name | Value |

+-----------------+-------+

| event_scheduler | ON |

+-----------------+-------+

1 row in set (0.01 sec)

从新创建定时器，执行成功：

mysql> CREATE PROCEDURE test1()

-> BEGIN

-> INSERT INTO tb01(username,password,create_time) values(‘李四‘, ‘张三‘,now());

-> END//

Query OK, 0 rows affected (0.01 sec)

mysql> CREATE EVENT test1

-> ON SCHEDULE EVERY 5 second STARTS TIMESTAMP ‘2019-08-16 17:34:22‘

-> ON COMPLETION PRESERVE

-> DO

-> BEGIN

-> CALL test1();

-> END//

Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;

mysql> select now();