笔者系统为 mac ，不知怎的，Mysql 竟然报如下错误：

ERROR 1449 (HY000): The user specified as a definer ('mysql.infoschema'@'localhost') does not exist

一时没有找到是什么操作导致的这个错误。然后经过查询，参考文章
解决了问题。

登录

$ mysql -uroot -p12345678
$ mysql> show databases;
ERROR 1449 (HY000): The user specified as a definer ('mysql.infoschema'@'localhost') does not exist

修改

$ mysql> SET GLOBAL innodb_fast_shutdown = 1;
Query OK, 0 rows affected (0.01 sec)
$ mysql> quit
Bye

更新

$ mysql_upgrade -uroot -p12345678
mysql_upgrade: [Warning] Using a password on the command line interface can be insecure.
Checking if update is needed.
Checking server version.
Running queries to upgrade MySQL server.
Upgrading system table data.
Checking system database.
mysql.columns_priv                                 OK
mysql.component                                    OK
……
yn.roles                                           OK
yn.users                                           OK
Upgrade process completed successfully.
Checking if update is needed.

重新登录之后，服务恢复正常。