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8.2.1 `myisamchk' General Options
---------------------------------
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.
* -help, -?
Display a help message and exit.
* -debug=DEBUG_OPTIONS, -# DEBUG_OPTIONS
Write a debugging log. The DEBUG_OPTIONS string often is
`'d:t:o,FILE_NAME''.
* -silent, -s
Silent mode. Write output only when errors occur. You can use -s
twice (-ss) to make `myisamchk' very silent.
* -verbose, -v
Verbose mode. Print more information about what the program does.
This can be used with -d and -e. Use -v multiple times (-vv, -vvv)
for even more output.
* -version, -V
Display version information and exit.
* -wait, -w
Instead of terminating with an error if the table is locked, wait
until the table is unlocked before continuing. Note that 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 -VAR_NAME=VALUE
syntax:
*Variable* *Default Value*
`decode_bits' 9
`ft_max_word_len' version-dependent
`ft_min_word_len' 4
`ft_stopword_file' built-in list
`key_buffer_size' 523264
`myisam_block_size' 1024
`read_buffer_size' 262136
`sort_buffer_size' 2097144
`sort_key_blocks' 16
`stats_method' nulls_unequal
`write_buffer_size' 262136
The possible `myisamchk' variables and their default values can be
examined with `myisamchk --help':
`sort_buffer_size' is used when the keys are repaired by sorting keys,
which is the normal case when you use -recover.
`key_buffer_size' is used when you are checking the table with
-extend-check or 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:
* You use -safe-recover.
* 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 `CHAR',
`VARCHAR', or `TEXT' columns, 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 -sort-recover option.
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 `key_buffer_size' and
`sort_buffer_size' variables 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_size' is the size used for index blocks.
`stats_method' influences how `NULL' values are treated for index
statistics collection when the -analyze option is given. It acts like
the `myisam_stats_method' system variable. For more information, see
the description of `myisam_stats_method' in
server-system-variables, and myisam-index-statistics. For
MySQL 5.0, `stats_method' was added in MySQL 5.0.14. For older
versions, the statistics collection method is equivalent to
`nulls_equal'.
`ft_min_word_len' and `ft_max_word_len' indicate the minimum and
maximum word length for `FULLTEXT' indexes. `ft_stopword_file' names
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 `FULLTEXT' indexes 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 `MyISAM' index 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_min_word_len',
`ft_max_word_len', and `ft_stopword_file' values 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:
shell> myisamchk --recover --ft_min_word_len=3 TBL_NAME.MYI
To ensure that `myisamchk' and the server use the same values for
full-text parameters, you can place each one in both the `[mysqld]' and
`[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 `REPAIR TABLE',
`ANALYZE TABLE', `OPTIMIZE TABLE', or `ALTER TABLE'. These statements
are performed by the server, which knows the proper full-text parameter
values to use.
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