myisamchk supports the following options for
table repair operations (operations performed when an option
such as --recover
or
--safe-recover
is given):
--backup
,-B
Command-Line Format --backup
Make a backup of the
.MYD
file asfile_name
-time
.BAK-
Command-Line Format --character-sets-dir=path
Type String Default Value [none]
The directory where character sets are installed. See Section 12.15, “Character Set Configuration”.
-
Command-Line Format --correct-checksum
Correct the checksum information for the table.
--data-file-length=
,len
-D
len
Command-Line Format --data-file-length=len
Type Numeric The maximum length of the data file (when re-creating data file when it is “full”).
--extend-check
,-e
Command-Line Format --extend-check
Do a repair that tries to recover every possible row from the data file. Normally, this also finds a lot of garbage rows. Do not use this option unless you are desperate.
See also the description of this option under table checking options.
For a description of the output format, see Section 6.6.4.5, “Obtaining Table Information with myisamchk”.
--force
,-f
Command-Line Format --force
Overwrite old intermediate files (files with names like
) instead of aborting.tbl_name
.TMD--keys-used=
,val
-k
val
Command-Line Format --keys-used=val
Type Numeric For myisamchk, the option value is a bit value that indicates which indexes to update. Each binary bit of the option value corresponds to a table index, where the first index is bit 0. An option value of 0 disables updates to all indexes, which can be used to get faster inserts. Deactivated indexes can be reactivated by using myisamchk -r.
-
Command-Line Format --max-record-length=len
Type Numeric Skip rows larger than the given length if myisamchk cannot allocate memory to hold them.
-
Command-Line Format --parallel-recover
NoteThis option is deprecated in MySQL 8.0.28 and removed in MySQL 8.0.30.
Use the same technique as
-r
and-n
, but create all the keys in parallel, using different threads. This is beta-quality code. Use at your own risk! --quick
,-q
Command-Line Format --quick
Achieve a faster repair by modifying only the index file, not the data file. You can specify this option twice to force myisamchk to modify the original data file in case of duplicate keys.
--recover
,-r
Command-Line Format --recover
Do a repair that can fix almost any problem except unique keys that are not unique (which is an extremely unlikely error with
MyISAM
tables). If you want to recover a table, this is the option to try first. You should try--safe-recover
only if myisamchk reports that the table cannot be recovered using--recover
. (In the unlikely case that--recover
fails, the data file remains intact.)If you have lots of memory, you should increase the value of
myisam_sort_buffer_size
.--safe-recover
,-o
Command-Line Format --safe-recover
Do a repair using an old recovery method that reads through all rows in order and updates all index trees based on the rows found. This is an order of magnitude slower than
--recover
, but can handle a couple of very unlikely cases that--recover
cannot. This recovery method also uses much less disk space than--recover
. Normally, you should repair first using--recover
, and then with--safe-recover
only if--recover
fails.If you have lots of memory, you should increase the value of
key_buffer_size
.-
Command-Line Format --set-collation=name
Type String Specify the collation to use for sorting table indexes. The character set name is implied by the first part of the collation name.
--sort-recover
,-n
Command-Line Format --sort-recover
Force myisamchk to use sorting to resolve the keys even if the temporary files would be very large.
--tmpdir=
,dir_name
-t
dir_name
Command-Line Format --tmpdir=dir_name
Type Directory name The path of the directory to be used for storing temporary files. If this is not set, myisamchk uses the value of the
TMPDIR
environment variable.--tmpdir
can be set to a list of directory paths that are used successively in round-robin fashion for creating temporary files. The separator character between directory names is the colon (:
) on Unix and the semicolon (;
) on Windows.--unpack
,-u
Command-Line Format --unpack
Unpack a table that was packed with myisampack.