前陣子將mysql資料庫由5.5.14升級到5.6.36，升級後所有的業務資料都正常。運行了幾天後，發現在主庫上新增使用者失敗，錯誤提示為：ERROR 1805 (HY000): Column count of mysql.user is wrong，提示mysql.user表列的數目不對。還真是個坑。下面是其解決方案。

一、故障現象

mysql> create user 'henry'@'localhost' identified by 'password';
ERROR 1805 (HY000): Column count of mysql.user is wrong. Expected 43
 
, found 42. The table is probably corrupted

使用grant all privileges 方式建立使用者時收到跟上述一樣的錯誤。提示列的數目不對。

二、排錯及解決故障

從上面的描述來看，說列的數目不對，因此我們升級後環境mysql.user表的建表語句
([email protected])[(none)]>show variables like 'version';
+---------------+------------+
| Variable_name | Value |
+---------------+------------+
 

| version | 5.5.14-log |
+---------------+------------+
1 row in set (0.01 sec)

([email protected])[(none)]>show create table mysql.user\G
*************************** 1. row ***************************
Table: user
Create Table: CREATE TABLE `user` (
`Host` char(60) COLLATE utf8_bin NOT NULL DEFAULT '
 
',
............
`plugin` char(64) COLLATE utf8_bin DEFAULT '',
`authentication_string` text COLLATE utf8_bin,
PRIMARY KEY (`Host`,`User`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Users and global privileges'

安裝一個新的mysql 5.6.36後檢視mysql.user表的建表語句
mysql> show variables like 'version';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| version | 5.6.36 |
+---------------+--------+
1 row in set (0.01 sec)

mysql> show create table mysql.user\G
*************************** 1. row ***************************
Table: user
Create Table: CREATE TABLE `user` (
...........
`plugin` char(64) COLLATE utf8_bin DEFAULT 'mysql_native_password',
`authentication_string` text COLLATE utf8_bin,
`password_expired` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
PRIMARY KEY (`Host`,`User`)   ---上行為多出的列，即先前使用主從複製時password_expired列沒有
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Users and global privileges'

--為升級後的mysql 5.6.36手工新增這個password_expired列
mysql> alter table mysql.user add column `password_expired` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N';
Query OK, 10 rows affected (0.00 sec)
Records: 10 Duplicates: 0 Warnings: 0

--再次建立使用者成功
mysql> grant all privileges on *.* to 'henry'@'%' identified by 'henrypwd';
Query OK, 0 rows affected (0.00 sec)