myisampack

Compress MyISAM tables into read-only form that is typically 40 to 70 percent smaller with myisampack.

myisampack

myisampack is a tool for compressing MyISAM tables. The resulting tables are read-only, and usually about 40% to 70% smaller. It is run as follows:

myisampack [options] file_name [file_name2...]

The file_name is the .MYI index file. The extension can be omitted, although keeping it permits wildcards, such as:

myisampack *.MYI

...to compress all the files.

myisampack compresses each column separately, and, when the resulting data is read, only the individual rows and columns required need to be decompressed, allowing for quicker reading.

Once a table has been packed, use myisamchk -rq (the quick and recover options) to rebuild its indexes.

myisampack does not support partitioned tables or vector indexes.

Do not run myisampack if the tables could be updated during the operation, and skip_external_locking has been set.

Options

The following variables can be set while passed as command line options tomyisampack, or set with a [myisampack] section in your my.cnf file.

Option	Description
-b, --backup	Make a backup of the table as table_name.OLD.
--character-sets-dir=name	Directory where character sets are.
-
## , --debug[=name]	Output debug log. Often this is 'd:t:o,filename'.
-f, --force	Force packing of table even if it gets bigger or if tempfile exists.
-j, --join=name	Join all given tables into 'new_table_name'. All tables must have identical layouts.
-?, --help	Display help and exit.
-s, --silent	Only write output when an error occurs
-T, --tmpdir=name	Use temporary directory to store temporary table.
-t, --test	Don't pack table, only test packing it.
-v, --verbose	Write info about progress and packing result. Use multiple -v flags for more verbosity.
-V, --version	Output version information and exit.
-w, --wait	Wait and retry if table is in use.

Uncompressing

To uncompress a table compressed with myisampack, use the myisamchk -u option.

Examples

> myisampack /var/lib/mysql/test/posts
Compressing /var/lib/mysql/test/posts.MYD: (1680 records)
- Calculating statistics
- Compressing file
37.71%
> myisamchk -rq /var/lib/mysql/test/posts
- check record delete-chain
- recovering (with sort) MyISAM-table '/var/lib/mysql/test/posts'
Data records: 1680
- Fixing index 1
- Fixing index 2

See Also

• FLUSH TABLES FOR EXPORT

• myisamchk

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