myisampack
Contents
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.
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 commandline options to
myisampack, 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
