30.4. Repairing InnoDB Tables

30.4. Repairing InnoDB Tables

As mentioned earlier in this chapter, you can check InnoDB tables by using the CHECK TABLE statement or by using a client program that issues the statement for you. However, if an InnoDB table has problems, you cannot fix it by using REPAIR TABLE because that statement applies only to MyISAM.

If a table check indicates that an InnoDB table has problems, you should be able to restore the table to a consistent state by dumping it with mysqldump, dropping it, and re-creating it from the dump file:

 shell> mysqldump db_name table_name > dump_file shell> mysql db_name < dump_file 

In the event of a crash of the MySQL server or the host on which it runs, some InnoDB tables might need repairs. Normally, it suffices simply to restart the server because the InnoDB storage engine performs auto-recovery as part of its startup sequence. In rare cases, the server might not start up due to failure of InnoDB auto-recovery. If that happens, use the following procedure:

• Restart the server with the --innodb_force_recovery option set to a value in the range from 1 to 6. These values indicate increasing levels of caution in avoiding a crash, and increasing levels of tolerance for possible inconsistency in the recovered tables. A good value to start with is 4.
  
  
• When you start the server with --innodb_force_recovery set to a non-zero value, InnoDB treats the tablespace as read-only. Consequently, you should dump the InnoDB tables with mysqldump and then drop them while the option is in effect. Then restart the server without the --innodb_force_recovery option. When the server comes up, recover the InnoDB tables from the dump files.
  
  
• If the preceding steps fail, it's necessary to restore the InnoDB tables from a previous backup.