The options described in this section can be used for any type of table maintenance operation performed by myisamchk. The sections following this one describe options that pertain only to specific operations, such as table checking or repairing.
Display a help message and exit. Options are grouped by type of operation.
Display a help message and exit. Options are presented in a single list.
Write a debugging log. A typical
'd:t:o,. The default is
Silent mode. Write output only when errors occur. You can use
-ss) to make myisamchk very silent.
Verbose mode. Print more information about what the program does. This can be used with
-vmultiple times (
-vvv) for even more output.
Display version information and exit.
Instead of terminating with an error if the table is locked, wait until the table is unlocked before continuing. If you are running mysqld with external locking disabled, the table can be locked only by another myisamchk command.
You can also set the following variables by using
Variable Default Value
sort_buffer_sizeis used when the keys are repaired by sorting keys, which is the normal case when you use
key_buffer_sizeis used when you are checking the table with
--extend-checkor when the keys are repaired by inserting keys row by row into the table (like when doing normal inserts). Repairing through the key buffer is used in the following cases:
The temporary files needed to sort the keys would be more than twice as big as when creating the key file directly. This is often the case when you have large key values for
TEXTcolumns, because the sort operation needs to store the complete key values as it proceeds. If you have lots of temporary space and you can force myisamchk to repair by sorting, you can use the
Repairing through the key buffer takes much less disk space than using sorting, but is also much slower.
If you want a faster repair, set the
sort_buffer_sizevariables to about 25% of your available memory. You can set both variables to large values, because only one of them is used at a time.
myisam_block_sizeis the size used for index blocks.
NULLvalues are treated for index statistics collection when the
--analyzeoption is given. It acts like the
myisam_stats_methodsystem variable. For more information, see the description of
myisam_stats_methodin Section 5.1.4, “Server System Variables”, and Section 7.4.7, “
MyISAMIndex Statistics Collection”.
ft_max_word_lenindicate the minimum and maximum word length for
ft_stopword_filenames the stopword file. These need to be set under the following circumstances.
If you use myisamchk to perform an operation that modifies table indexes (such as repair or analyze), the
FULLTEXTindexes are rebuilt using the default full-text parameter values for minimum and maximum word length and the stopword file unless you specify otherwise. This can result in queries failing.
The problem occurs because these parameters are known only by the server. They are not stored in
MyISAMindex files. To avoid the problem if you have modified the minimum or maximum word length or the stopword file in the server, specify the same
ft_stopword_filevalues to myisamchk that you use for mysqld. For example, if you have set the minimum word length to 3, you can repair a table with myisamchk like this:
myisamchk --recover --ft_min_word_len=3
To ensure that myisamchk and the server use the same values for full-text parameters, you can place each one in both the
[myisamchk]sections of an option file:
[mysqld] ft_min_word_len=3 [myisamchk] ft_min_word_len=3
An alternative to using myisamchk is to use the
OPTIMIZE TABLE, or
ALTER TABLE. These statements are performed by the server, which knows the proper full-text parameter values to use.