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 12.4.2.3, “CHECK TABLE
Syntax”,
Section 12.4.2.6, “REPAIR TABLE
Syntax”, and
Section 4.6.2, “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 A.5.4.2, “What to Do If MySQL Keeps Crashing”, and
MySQL
Internals: Porting.
MySQL Enterprise. Find out about problems before they occur. Subscribe to the MySQL Enterprise Monitor for expert advice about the state of your servers. For more information, see http://www.mysql.com/products/enterprise/advisors.html.
User Comments
if you set
[mysqld]
ft_min_word_len=3
you should also set
[myisamchk]
ft_min_word_len=3
if you use myisamchk
I ran into a case where a large myiasm table threw the above error when it was included inside a transaction (by mistake) along with other innoDB tables. A bunch of mass deletes were taking place, and the operation always ended with the table corrupted.
A quick conversion to innoDB solved the problem:
ALTER TABLE tablename TYPE=InnoDB;
Thanks for that! I had a tiny MyISAM table but, all the same, queries were sometimes taking too long to execute & the container page wouldn't load properly. Changed to INNO-DB, problem cleared!
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