Innodb 表修复

摘要:
      突然收到MySQL报警,从库的数据库挂了,一直在不停的重启,打开错误日志,发现有张表坏了。innodb表损坏不能通过repair table 等修复myisam的命令操作。现在记录下解决过程,下次遇到就不会这么手忙脚乱了。

处理过程:
    一遇到报警之后,直接打开错误日志,里面的信息:

InnoDB: Database page corruption on disk or a failed
InnoDB: file read of page 30506.
InnoDB: You may have to recover from a backup.
130509 20:33:48  InnoDB: Page dump in ascii and hex (16384 bytes):
##很多十六进制的代码
……
……
InnoDB: End of page dump
130509 20:37:34  InnoDB: Page checksum 1958578898, prior-to-4.0.14-form checksum 3765017239
InnoDB: stored checksum 3904709694, prior-to-4.0.14-form stored checksum 3765017239
InnoDB: Page lsn 5 614270220, low 4 bytes of lsn at page end 614270220
InnoDB: Page number (if stored to page already) 30506,
InnoDB: space id (if created with >= MySQL-4.1.1 and stored already) 19 InnoDB: Page may be an index page where index id is 54 InnoDB: (index "PRIMARY" of table "maitem"."email_status")
InnoDB: Database page corruption on disk or a failed InnoDB: file read of page 30506. InnoDB: You may have to recover from a backup. InnoDB: It is also possible that your operating InnoDB: system has corrupted its own file cache InnoDB: and rebooting your computer removes the InnoDB: error. InnoDB: If the corrupt page is an index page InnoDB: you can also try to fix the corruption InnoDB: by dumping, dropping, and reimporting InnoDB: the corrupt table. You can use CHECK InnoDB: TABLE to scan your table for corruption.
InnoDB: See also http://dev.mysql.com/doc/refman/5.5/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
InnoDB: A new raw disk partition was initialized or
InnoDB: innodb_force_recovery is on: we do not allow
InnoDB: database modifications by the user. Shut down
InnoDB: mysqld and edit my.cnf so that newraw is replaced
InnoDB: with raw, and innodb_force_... is removed.
130509 20:39:35 [Warning] Invalid (old?) table or database name '#sql2-19c4-5'

从错误日志里面很清楚的知道哪里出现了问题,该怎么处理。这时候数据库隔几s就重启,所以差不多可以说你是访问不了数据库的。所以马上想到要修复innodb表了。
以前在Performance的blog上看过类似文章。

当时想到的是在修复之前保证数据库正常,不是这么异常的无休止的重启。所以就修改了配置文件的一个参数:innodb_force_recovery

innodb_force_recovery影响整个InnoDB存储引擎的恢复状况。默认为0,表示当需要恢复时执行所有的

innodb_force_recovery可以设置为1-6,大的数字包含前面所有数字的影响。当设置参数值大于0后,可以对表进行select,create,drop操作,但insert,update或者delete这类操作是不允许的。

1(SRV_FORCE_IGNORE_CORRUPT):忽略检查到的corrupt页。 2(SRV_FORCE_NO_BACKGROUND):阻止主线程的运行,如主线程需要执行full purge操作,会导致crash。 3(SRV_FORCE_NO_TRX_UNDO):不执行事务回滚操作。 4(SRV_FORCE_NO_IBUF_MERGE):不执行插入缓冲的合并操作。 5(SRV_FORCE_NO_UNDO_LOG_SCAN):不查看重做日志,InnoDB存储引擎会将未提交的事务视为已提交。 6(SRV_FORCE_NO_LOG_REDO):不执行前滚的操作。

因为错误日志里面提示出现了坏页,导致数据库崩溃,所以这里把innodb_force_recovery 设置为1,忽略检查到的坏页。重启数据库之后,正常了,没有出现上面的错误信息。找到错误信息出现的表:
(index "PRIMARY" of table "maitem"."email_status")

数据页面的主键索引(clustered key index)被损坏。这种情况和数据的二级索引(secondary indexes)被损坏相比要糟很多,因为后者可以通过使用OPTIMIZE TABLE命令来修复,但这和更难以恢复的表格目录(table dictionary)被破坏的情况来说要好一些。

操作步骤:
因为被破坏的地方只在索引的部分,所以当使用innodb_force_recovery = 1运行InnoDB时,操作如下:

执行check,repair table 都无效
alter table email_status engine =myisam;  #也报错了,因为模式是innodb_force_recovery =1
ERROR 1025 (HY000): Error on rename of '...' to '....' (errno: -1)
建立一张表: create table email_status_bak   #和原表结构一样,只是把INNODB改成了MYISAM。 把数据导进去:#写不进去则需要把注释掉innodb_force_recovery 之后,重启 insert into email_status_bak select * from email_status;

删除掉原表:
drop table email_status;
注释掉innodb_force_recovery 之后,重启。上面做了,这里就不需要了。 重命名: rename
table email_status_bak to email_status;

最后改回INNODB存储引擎 alter table
email_status engine = innodb


注意:
在MySQL 5.5可以修改 innodb_purge_threads 的版本中(5.1版本不能修改该参数),innodb_purge_threads 和 innodb_force_recovery一起设置会出现一种loop现象

130510 18:13:23  InnoDB: Waiting for the background threads to start
130510 18:13:24  InnoDB: Waiting for the background threads to start
130510 18:13:25  InnoDB: Waiting for the background threads to start
130510 18:13:26  InnoDB: Waiting for the background threads to start
130510 18:13:27  InnoDB: Waiting for the background threads to start
130510 18:13:28  InnoDB: Waiting for the background threads to start
130510 18:13:29  InnoDB: Waiting for the background threads to start
130510 18:13:30  InnoDB: Waiting for the background threads to start
130510 18:13:31  InnoDB: Waiting for the background threads to start
130510 18:13:32  InnoDB: Waiting for the background threads to start
130510 18:13:33  InnoDB: Waiting for the background threads to start
…………
…………

数据库无法启动,现象出现的条件是:mysql 版本 5.5
innodb_purge_threads =1,innodb_force_recovery >1 的情况(=1 没有问题),所以当需要设置innodb_force_recovery>1的时候需要关闭 innodb_purge_threads,设置他=0(默认)

原因是:

mysql 原代码的脚本:
  while (srv_shutdown_state == SRV_SHUTDOWN_NONE) { 
      if (srv_thread_has_reserved_slot(SRV_MASTER) == ULINT_UNDEFINED 
          || (srv_n_purge_threads == 1 
          && srv_thread_has_reserved_slot(SRV_WORKER) 
          == ULINT_UNDEFINED)) { 

          ut_print_timestamp(stderr); 
          fprintf(stderr, "  InnoDB: " 
              "Waiting for the background threads to " 
              "start\n"); 
          os_thread_sleep(1000000); 
      } else { 
          break; 
      } 
  }  


总结:

      这里的一个重要知识点就是 对 innodb_force_recovery 参数的理解了,要是遇到数据损坏甚至是其他的损坏。可能上面的方法不行了,需要尝试另一个方法:insert into tb select * from ta limit X;甚至是dump出去,再load回来。更多的修复方法请看 :
1: Recovering Innodb table Corruption
2:恢复损坏的InnoDB表格
3:MySQL Data Recovery

 

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