MYISAM索引文件損壞的修復方法

使用MYISAM存儲引擎，當創建一個表時，會出現三個文件：數據文件MYD，索引文件MYI,格式文件frm。當索引文件損壞時或者丟失時，可以用如下的方法進行修復。下面是實驗過程。

[mysql@testapp74 notify]$ mv message_ignore.MYI message_ignore.MYI.bak
[mysql@testapp74 notify]$
[mysql@testapp74 notify]$ mysqld_safe &
[1] 26267
[mysql@testapp74 notify]$ 080630 14:19:03 mysqld_safe Logging to '/usr/mysql_data/log/alert.log'.
080630 14:19:03 mysqld_safe Starting mysqld daemon with databases from /usr/mysql_data/data
[mysql@testapp74 notify]$
[mysql@testapp74 notify]$
[mysql@testapp74 notify]$
[mysql@testapp74 notify]$ vi /usr/mysql_data/log/alert.log
080630 14:18:14 [Note] /usr/sbin/mysqld: Normal shutdown
080630 14:18:14 [Note] Event Scheduler: Purging the queue. 0 events
080630 14:18:16 InnoDB: Starting shutdown...
080630 14:18:19 InnoDB: Shutdown completed; log sequence number 162 783173592
080630 14:18:19 [Note] /usr/sbin/mysqld: Shutdown complete
080630 14:18:19 mysqld_safe mysqld from pid file /usr/mysql_data/data/testapp74.pid ended
080630 14:19:03 mysqld_safe Starting mysqld daemon with databases from /usr/mysql_data/data
080630 14:19:03 InnoDB: Started; log sequence number 162 783173592
080630 14:19:03 [Note] Event Scheduler: Loaded 0 events
080630 14:19:03 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.1.23-rc-community' socket: '/tmp/mysql.sock' port: 3306 MySQL Community Edition (GPL)

從上面可以看出，當一個表出現問題，mysql的警告日志並沒有任何的錯誤出現。

[mysql@testapp74 notify]$ mysql -uroot
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.1.23-rc-community MySQL Community Edition (GPL)
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> use notify
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql>
mysql>
mysql>
mysql>
mysql> select * from message_ignore limit 1; --當查詢表時，會報錯
ERROR 1017 (HY000): Can't find file: 'message_ignore' (errno: 2)
mysql> check table message_ignore;
+-----------------------+-------+----------+----------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+-----------------------+-------+----------+----------------------------------------------+
| notify.message_ignore | check | Error | Can't find file: 'message_ignore' (errno: 2) |
| notify.message_ignore | check | error | Corrupt |
+-----------------------+-------+----------+----------------------------------------------+
2 rows in set (0.03 sec)
mysql>
mysql> repair table message_ignore;
+-----------------------+--------+----------+----------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+-----------------------+--------+----------+----------------------------------------------+
| notify.message_ignore | repair | Error | Can't find file: 'message_ignore' (errno: 2) |
| notify.message_ignore | repair | error | Corrupt |
+-----------------------+--------+----------+----------------------------------------------+
2 rows in set (0.00 sec)

使用格式化文件frm重新創建索引文件

mysql> repair table message_ignore USE_FRM;
+-----------------------+--------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+-----------------------+--------+----------+----------+
| notify.message_ignore | repair | status | OK |
+-----------------------+--------+----------+----------+
1 row in set (0.02 sec)
mysql>
mysql> check table message_ignore;
+-----------------------+-------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+-----------------------+-------+----------+----------+
| notify.message_ignore | check | status | OK |
+-----------------------+-------+----------+----------+
1 row in set (0.02 sec)

修復後，數據可以正常查詢mysql> select * from message_ignore limit 1;
Empty set (0.00 sec)

如果是格式化文件frm損壞，可以從slave拷貝過來即可，或者從備份中恢復。