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MYISAMPACK(1)		     MySQL Database System		 MYISAMPACK(1)

NAME
       myisampack - generate compressed, read-only MyISAM tables

SYNOPSIS
       myisampack [options] file_name ...

DESCRIPTION
       The myisampack utility compresses MyISAM	tables.	 myisampack works by
       compressing each	column in the table separately.	Usually, myisampack
       packs the data file 40% to 70%.

       When the	table is used later, the server	reads into memory the
       information needed to decompress	columns. This results in much better
       performance when	accessing individual rows, because you only have to
       uncompress exactly one row.

       MySQL uses mmap() when possible to perform memory mapping on compressed
       tables. If mmap() does not work,	MySQL falls back to normal read/write
       file operations.

       Please note the following:

       o   If the mysqld server	was invoked with external locking disabled, it
	   is not a good idea to invoke	myisampack if the table	might be
	   updated by the server during	the packing process. It	is safest to
	   compress tables with	the server stopped.

       o   After packing a table, it becomes read only.	This is	generally
	   intended (such as when accessing packed tables on a CD).

       o   myisampack does not support partitioned tables.

       Invoke myisampack like this:

	   shell> myisampack [options] file_name ...

       Each file name argument should be the name of an	index (.MYI) file. If
       you are not in the database directory, you should specify the path name
       to the file. It is permissible to omit the .MYI extension.

       After you compress a table with myisampack, use myisamchk -rq to
       rebuild its indexes.  myisamchk(1).

       myisampack supports the following options. It also reads	option files
       and supports the	options	for processing them described at
       Section 5.2.7, "Command-Line Options that Affect	Option-File Handling".

       o   --help, -?

	   Display a help message and exit.

       o   --backup, -b

	   Make	a backup of each table's data file using the name
	   tbl_name.OLD.

       o   --character-sets-dir=dir_name

	   The directory where character sets are installed. See Section 11.5,
	   "Character Set Configuration".

       o   --debug[=debug_options], -# [debug_options]

	   Write a debugging log. A typical debug_options string is
	   d:t:o,file_name. The	default	is d:t:o.

       o   --force, -f

	   Produce a packed table even if it becomes larger than the original
	   or if the intermediate file from an earlier invocation of
	   myisampack exists. (myisampack creates an intermediate file named
	   tbl_name.TMD	in the database	directory while	it compresses the
	   table. If you kill myisampack, the .TMD file	might not be deleted.)
	   Normally, myisampack	exits with an error if it finds	that
	   tbl_name.TMD	exists.	With --force, myisampack packs the table
	   anyway.

       o   --join=big_tbl_name,	-j big_tbl_name

	   Join	all tables named on the	command	line into a single packed
	   table big_tbl_name. All tables that are to be combined must have
	   identical structure (same column names and types, same indexes, and
	   so forth).

	   big_tbl_name	must not exist prior to	the join operation. All	source
	   tables named	on the command line to be merged into big_tbl_name
	   must	exist. The source tables are read for the join operation but
	   not modified.

       o   --silent, -s

	   Silent mode.	Write output only when errors occur.

       o   --test, -t

	   Do not actually pack	the table, just	test packing it.

       o   --tmpdir=dir_name, -T dir_name

	   Use the named directory as the location where myisampack creates
	   temporary files.

       o   --verbose, -v

	   Verbose mode. Write information about the progress of the packing
	   operation and its result.

       o   --version, -V

	   Display version information and exit.

       o   --wait, -w

	   Wait	and retry if the table is in use. If the mysqld	server was
	   invoked with	external locking disabled, it is not a good idea to
	   invoke myisampack if	the table might	be updated by the server
	   during the packing process.

       The following sequence of commands illustrates a	typical	table
       compression session:

	   shell> ls -l	station.*
	   -rw-rw-r--	1 monty	   my	      994128 Apr 17 19:00 station.MYD
	   -rw-rw-r--	1 monty	   my	       53248 Apr 17 19:00 station.MYI
	   -rw-rw-r--	1 monty	   my		5767 Apr 17 19:00 station.frm
	   shell> myisamchk -dvv station
	   MyISAM file:	    station
	   Isam-version:  2
	   Creation time: 1996-03-13 10:08:58
	   Recover time:  1997-02-02  3:06:43
	   Data	records:	      1192  Deleted blocks:		 0
	   Datafile parts:	      1192  Deleted data:		 0
	   Datafile pointer (bytes):	 2  Keyfile pointer (bytes):	 2
	   Max datafile	length:	  54657023  Max	keyfile	length:	  33554431
	   Recordlength:	       834
	   Record format: Fixed	length
	   table description:
	   Key Start Len Index	 Type		      Root  Blocksize	 Rec/key
	   1   2     4	 unique	 unsigned long	      1024	 1024	       1
	   2   32    30	 multip. text		     10240	 1024	       1
	   Field Start Length Type
	   1	 1     1
	   2	 2     4
	   3	 6     4
	   4	 10    1
	   5	 11    20
	   6	 31    1
	   7	 32    30
	   8	 62    35
	   9	 97    35
	   10	 132   35
	   11	 167   4
	   12	 171   16
	   13	 187   35
	   14	 222   4
	   15	 226   16
	   16	 242   20
	   17	 262   20
	   18	 282   20
	   19	 302   30
	   20	 332   4
	   21	 336   4
	   22	 340   1
	   23	 341   8
	   24	 349   8
	   25	 357   8
	   26	 365   2
	   27	 367   2
	   28	 369   4
	   29	 373   4
	   30	 377   1
	   31	 378   2
	   32	 380   8
	   33	 388   4
	   34	 392   4
	   35	 396   4
	   36	 400   4
	   37	 404   1
	   38	 405   4
	   39	 409   4
	   40	 413   4
	   41	 417   4
	   42	 421   4
	   43	 425   4
	   44	 429   20
	   45	 449   30
	   46	 479   1
	   47	 480   1
	   48	 481   79
	   49	 560   79
	   50	 639   79
	   51	 718   79
	   52	 797   8
	   53	 805   1
	   54	 806   1
	   55	 807   20
	   56	 827   4
	   57	 831   4
	   shell> myisampack station.MYI
	   Compressing station.MYI: (1192 records)
	   - Calculating statistics
	   normal:     20  empty-space:	  16  empty-zero:     12  empty-fill:  11
	   pre-space:	0  end-space:	  12  table-lookups:   5  zero:		7
	   Original trees:  57	After join: 17
	   - Compressing file
	   87.14%
	   Remember to run myisamchk -rq on compressed tables
	   shell> myisamchk -rq	station
	   - check record delete-chain
	   - recovering	(with sort) MyISAM-table 'station'
	   Data	records: 1192
	   - Fixing index 1
	   - Fixing index 2
	   shell> mysqladmin -uroot flush-tables
	   shell> ls -l	station.*
	   -rw-rw-r--	1 monty	   my	      127874 Apr 17 19:00 station.MYD
	   -rw-rw-r--	1 monty	   my	       55296 Apr 17 19:04 station.MYI
	   -rw-rw-r--	1 monty	   my		5767 Apr 17 19:00 station.frm
	   shell> myisamchk -dvv station
	   MyISAM file:	    station
	   Isam-version:  2
	   Creation time: 1996-03-13 10:08:58
	   Recover time:  1997-04-17 19:04:26
	   Data	records:	       1192  Deleted blocks:		  0
	   Datafile parts:	       1192  Deleted data:		  0
	   Datafile pointer (bytes):	  3  Keyfile pointer (bytes):	  1
	   Max datafile	length:	   16777215  Max keyfile length:     131071
	   Recordlength:		834
	   Record format: Compressed
	   table description:
	   Key Start Len Index	 Type		      Root  Blocksize	 Rec/key
	   1   2     4	 unique	 unsigned long	     10240	 1024	       1
	   2   32    30	 multip. text		     54272	 1024	       1
	   Field Start Length Type			   Huff	tree  Bits
	   1	 1     1      constant				   1	 0
	   2	 2     4      zerofill(1)			   2	 9
	   3	 6     4      no zeros,	zerofill(1)		   2	 9
	   4	 10    1					   3	 9
	   5	 11    20     table-lookup			   4	 0
	   6	 31    1					   3	 9
	   7	 32    30     no endspace, not_always		   5	 9
	   8	 62    35     no endspace, not_always, no empty	   6	 9
	   9	 97    35     no empty				   7	 9
	   10	 132   35     no endspace, not_always, no empty	   6	 9
	   11	 167   4      zerofill(1)			   2	 9
	   12	 171   16     no endspace, not_always, no empty	   5	 9
	   13	 187   35     no endspace, not_always, no empty	   6	 9
	   14	 222   4      zerofill(1)			   2	 9
	   15	 226   16     no endspace, not_always, no empty	   5	 9
	   16	 242   20     no endspace, not_always		   8	 9
	   17	 262   20     no endspace, no empty		   8	 9
	   18	 282   20     no endspace, no empty		   5	 9
	   19	 302   30     no endspace, no empty		   6	 9
	   20	 332   4      always zero			   2	 9
	   21	 336   4      always zero			   2	 9
	   22	 340   1					   3	 9
	   23	 341   8      table-lookup			   9	 0
	   24	 349   8      table-lookup			  10	 0
	   25	 357   8      always zero			   2	 9
	   26	 365   2					   2	 9
	   27	 367   2      no zeros,	zerofill(1)		   2	 9
	   28	 369   4      no zeros,	zerofill(1)		   2	 9
	   29	 373   4      table-lookup			  11	 0
	   30	 377   1					   3	 9
	   31	 378   2      no zeros,	zerofill(1)		   2	 9
	   32	 380   8      no zeros				   2	 9
	   33	 388   4      always zero			   2	 9
	   34	 392   4      table-lookup			  12	 0
	   35	 396   4      no zeros,	zerofill(1)		  13	 9
	   36	 400   4      no zeros,	zerofill(1)		   2	 9
	   37	 404   1					   2	 9
	   38	 405   4      no zeros				   2	 9
	   39	 409   4      always zero			   2	 9
	   40	 413   4      no zeros				   2	 9
	   41	 417   4      always zero			   2	 9
	   42	 421   4      no zeros				   2	 9
	   43	 425   4      always zero			   2	 9
	   44	 429   20     no empty				   3	 9
	   45	 449   30     no empty				   3	 9
	   46	 479   1					  14	 4
	   47	 480   1					  14	 4
	   48	 481   79     no endspace, no empty		  15	 9
	   49	 560   79     no empty				   2	 9
	   50	 639   79     no empty				   2	 9
	   51	 718   79     no endspace			  16	 9
	   52	 797   8      no empty				   2	 9
	   53	 805   1					  17	 1
	   54	 806   1					   3	 9
	   55	 807   20     no empty				   3	 9
	   56	 827   4      no zeros,	zerofill(2)		   2	 9
	   57	 831   4      no zeros,	zerofill(1)		   2	 9

       myisampack displays the following kinds of information:

       o   normal

	   The number of columns for which no extra packing is used.

       o   empty-space

	   The number of columns containing values that	are only spaces. These
	   occupy one bit.

       o   empty-zero

	   The number of columns containing values that	are only binary	zeros.
	   These occupy	one bit.

       o   empty-fill

	   The number of integer columns that do not occupy the	full byte
	   range of their type.	These are changed to a smaller type. For
	   example, a BIGINT column (eight bytes) can be stored	as a TINYINT
	   column (one byte) if	all its	values are in the range	from -128 to
	   127.

       o   pre-space

	   The number of decimal columns that are stored with leading spaces.
	   In this case, each value contains a count for the number of leading
	   spaces.

       o   end-space

	   The number of columns that have a lot of trailing spaces. In	this
	   case, each value contains a count for the number of trailing
	   spaces.

       o   table-lookup

	   The column had only a small number of different values, which were
	   converted to	an ENUM	before Huffman compression.

       o   zero

	   The number of columns for which all values are zero.

       o   Original trees

	   The initial number of Huffman trees.

       o   After join

	   The number of distinct Huffman trees	left after joining trees to
	   save	some header space.

       After a table has been compressed, the Field lines displayed by
       myisamchk -dvv include additional information about each	column:

       o   Type

	   The data type. The value may	contain	any of the following
	   descriptors:

	   o   constant

	       All rows	have the same value.

	   o   no endspace

	       Do not store endspace.

	   o   no endspace, not_always

	       Do not store endspace and do not	do endspace compression	for
	       all values.

	   o   no endspace, no empty

	       Do not store endspace. Do not store empty values.

	   o   table-lookup

	       The column was converted	to an ENUM.

	   o   zerofill(N)

	       The most	significant N bytes in the value are always 0 and are
	       not stored.

	   o   no zeros

	       Do not store zeros.

	   o   always zero

	       Zero values are stored using one	bit.

       o   Huff	tree

	   The number of the Huffman tree associated with the column.

       o   Bits

	   The number of bits used in the Huffman tree.

       After you run myisampack, use myisamchk to re-create any	indexes. At
       this time, you can also sort the	index blocks and create	statistics
       needed for the MySQL optimizer to work more efficiently:

	   shell> myisamchk -rq	--sort-index --analyze tbl_name.MYI

       After you have installed	the packed table into the MySQL	database
       directory, you should execute mysqladmin	flush-tables to	force mysqld
       to start	using the new table.

       To unpack a packed table, use the --unpack option to myisamchk.

COPYRIGHT
       Copyright (C) 1997, 2016, Oracle	and/or its affiliates. All rights
       reserved.

       This documentation is free software; you	can redistribute it and/or
       modify it only under the	terms of the GNU General Public	License	as
       published by the	Free Software Foundation; version 2 of the License.

       This documentation is distributed in the	hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A	PARTICULAR PURPOSE. See	the GNU
       General Public License for more details.

       You should have received	a copy of the GNU General Public License along
       with the	program; if not, write to the Free Software Foundation,	Inc.,
       51 Franklin Street, Fifth Floor,	Boston,	MA 02110-1301 USA or see
       http://www.gnu.org/licenses/.

SEE ALSO
       For more	information, please refer to the MySQL Reference Manual, which
       may already be installed	locally	and which is also available online at
       http://dev.mysql.com/doc/.

AUTHOR
       Oracle Corporation (http://dev.mysql.com/).

MySQL 5.7			  09/28/2016			 MYISAMPACK(1)

NAME | SYNOPSIS | DESCRIPTION | COPYRIGHT | SEE ALSO | AUTHOR

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