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15.2.4.1 Corrupted MyISAM Tables

Even though the MyISAM table format is very reliable (all changes to a table made by an SQL statement are written before the statement returns), you can still get corrupted tables if any of the following events occur:

  • The mysqld process is killed in the middle of a write.

  • An unexpected computer shutdown occurs (for example, the computer is turned off).

  • Hardware failures.

  • You are using an external program (such as myisamchk) to modify a table that is being modified by the server at the same time.

  • A software bug in the MySQL or MyISAM code.

Typical symptoms of a corrupt table are:

  • You get the following error while selecting data from the table:

    Incorrect key file for table: '...'. Try to repair it
  • Queries don't find rows in the table or return incomplete results.

You can check the health of a MyISAM table using the CHECK TABLE statement, and repair a corrupted MyISAM table with REPAIR TABLE. When mysqld is not running, you can also check or repair a table with the myisamchk command. See Section 13.7.2.2, “CHECK TABLE Syntax”, Section 13.7.2.5, “REPAIR TABLE Syntax”, and Section 4.6.3, “myisamchk — MyISAM Table-Maintenance Utility”.

If your tables become corrupted frequently, you should try to determine why this is happening. The most important thing to know is whether the table became corrupted as a result of a server crash. You can verify this easily by looking for a recent restarted mysqld message in the error log. If there is such a message, it is likely that table corruption is a result of the server dying. Otherwise, corruption may have occurred during normal operation. This is a bug. You should try to create a reproducible test case that demonstrates the problem. See Section B.5.3.3, “What to Do If MySQL Keeps Crashing”, and Section 28.5, “Debugging and Porting MySQL”.


User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
  Posted by Piotr SaÅ‚aciak on December 11, 2010
When You are using a trigger (or triggers) with Your MyISAM tables they may be "unrepairable" when they become corrupted. In such a case, You should physically delete all trigger files from database directory (eventually run DROP TRIGGER command), then run REPAIR statement and finally define Your trigger again.
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