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'\" t
.\" Title: myisampack
.\" Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\" Date: 11/29/2021
.\" Manual: MySQL Database System
.\" Source: MySQL 5.7
.\" Language: English
.\"
.TH "MYISAMPACK" "1" "11/29/2021" "MySQL 5\&.7" "MySQL Database System"
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.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
myisampack \- generate compressed, read\-only MyISAM tables
.SH "SYNOPSIS"
.HP \w'\fBmyisampack\ [\fR\fB\fIoptions\fR\fR\fB]\ \fR\fB\fIfile_name\fR\fR\fB\ \&.\&.\&.\fR\ 'u
\fBmyisampack [\fR\fB\fIoptions\fR\fR\fB] \fR\fB\fIfile_name\fR\fR\fB \&.\&.\&.\fR
.SH "DESCRIPTION"
.PP
The
\fBmyisampack\fR
utility compresses
MyISAM
tables\&.
\fBmyisampack\fR
works by compressing each column in the table separately\&. Usually,
\fBmyisampack\fR
packs the data file 40% to 70%\&.
.PP
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\&.
.PP
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\&.
.PP
Please note the following:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
If the
\fBmysqld\fR
server was invoked with external locking disabled, it is not a good idea to invoke
\fBmyisampack\fR
if the table might be updated by the server during the packing process\&. It is safest to compress tables with the server stopped\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
After packing a table, it becomes read only\&. This is generally intended (such as when accessing packed tables on a CD)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fBmyisampack\fR
does not support partitioned tables\&.
.RE
.PP
Invoke
\fBmyisampack\fR
like this:
.sp
.if n \{\
.RS 4
.\}
.nf
myisampack [\fIoptions\fR] \fIfile_name\fR \&.\&.\&.
.fi
.if n \{\
.RE
.\}
.PP
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\&.
.PP
After you compress a table with
\fBmyisampack\fR, use
\fBmyisamchk \-rq\fR
to rebuild its indexes\&.
myisamchk(1)\&.
.PP
\fBmyisampack\fR
supports the following options\&. It also reads option files and supports the options for processing them described at
Section\ \&4.2.2.3, \(lqCommand-Line Options that Affect Option-File Handling\(rq\&.
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-help\fR,
\fB\-?\fR
Display a help message and exit\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-backup\fR,
\fB\-b\fR
Make a backup of each table\*(Aqs data file using the name
\fItbl_name\fR\&.OLD\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-character\-sets\-dir=\fR\fB\fIdir_name\fR\fR
The directory where character sets are installed\&. See
Section\ \&10.15, \(lqCharacter Set Configuration\(rq\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-debug[=\fR\fB\fIdebug_options\fR\fR\fB]\fR,
\fB\-# [\fR\fB\fIdebug_options\fR\fR\fB]\fR
Write a debugging log\&. A typical
\fIdebug_options\fR
string is
d:t:o,\fIfile_name\fR\&. The default is
d:t:o\&.
.sp
This option is available only if MySQL was built using
\fBWITH_DEBUG\fR\&. MySQL release binaries provided by Oracle are
\fInot\fR
built using this option\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-force\fR,
\fB\-f\fR
Produce a packed table even if it becomes larger than the original or if the intermediate file from an earlier invocation of
\fBmyisampack\fR
exists\&. (\fBmyisampack\fR
creates an intermediate file named
\fItbl_name\fR\&.TMD
in the database directory while it compresses the table\&. If you kill
\fBmyisampack\fR, the
\&.TMD
file might not be deleted\&.) Normally,
\fBmyisampack\fR
exits with an error if it finds that
\fItbl_name\fR\&.TMD
exists\&. With
\fB\-\-force\fR,
\fBmyisampack\fR
packs the table anyway\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-join=\fR\fB\fIbig_tbl_name\fR\fR,
\fB\-j \fR\fB\fIbig_tbl_name\fR\fR
Join all tables named on the command line into a single packed table
\fIbig_tbl_name\fR\&. All tables that are to be combined
\fImust\fR
have identical structure (same column names and types, same indexes, and so forth)\&.
.sp
\fIbig_tbl_name\fR
must not exist prior to the join operation\&. All source tables named on the command line to be merged into
\fIbig_tbl_name\fR
must exist\&. The source tables are read for the join operation but not modified\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-silent\fR,
\fB\-s\fR
Silent mode\&. Write output only when errors occur\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-test\fR,
\fB\-t\fR
Do not actually pack the table, just test packing it\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-tmpdir=\fR\fB\fIdir_name\fR\fR,
\fB\-T \fR\fB\fIdir_name\fR\fR
Use the named directory as the location where
\fBmyisampack\fR
creates temporary files\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-verbose\fR,
\fB\-v\fR
Verbose mode\&. Write information about the progress of the packing operation and its result\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-version\fR,
\fB\-V\fR
Display version information and exit\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-\-wait\fR,
\fB\-w\fR
Wait and retry if the table is in use\&. If the
\fBmysqld\fR
server was invoked with external locking disabled, it is not a good idea to invoke
\fBmyisampack\fR
if the table might be updated by the server during the packing process\&.
.RE
.PP
The following sequence of commands illustrates a typical table compression session:
.sp
.if n \{\
.RS 4
.\}
.nf
$> \fBls \-l station\&.*\fR
\-rw\-rw\-r\-\- 1 jones my 994128 Apr 17 19:00 station\&.MYD
\-rw\-rw\-r\-\- 1 jones my 53248 Apr 17 19:00 station\&.MYI
\-rw\-rw\-r\-\- 1 jones my 5767 Apr 17 19:00 station\&.frm
$> \fBmyisamchk \-dvv station\fR
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
$> \fBmyisampack station\&.MYI\fR
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
$> \fBmyisamchk \-rq station\fR
\- check record delete\-chain
\- recovering (with sort) MyISAM\-table \*(Aqstation\*(Aq
Data records: 1192
\- Fixing index 1
\- Fixing index 2
$> \fBmysqladmin \-uroot flush\-tables\fR
$> \fBls \-l station\&.*\fR
\-rw\-rw\-r\-\- 1 jones my 127874 Apr 17 19:00 station\&.MYD
\-rw\-rw\-r\-\- 1 jones my 55296 Apr 17 19:04 station\&.MYI
\-rw\-rw\-r\-\- 1 jones my 5767 Apr 17 19:00 station\&.frm
$> \fBmyisamchk \-dvv station\fR
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
.fi
.if n \{\
.RE
.\}
.PP
\fBmyisampack\fR
displays the following kinds of information:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
normal
.sp
The number of columns for which no extra packing is used\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
empty\-space
.sp
The number of columns containing values that are only spaces\&. These occupy one bit\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
empty\-zero
.sp
The number of columns containing values that are only binary zeros\&. These occupy one bit\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
empty\-fill
.sp
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\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
pre\-space
.sp
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\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
end\-space
.sp
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\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
table\-lookup
.sp
The column had only a small number of different values, which were converted to an
ENUM
before Huffman compression\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
zero
.sp
The number of columns for which all values are zero\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Original trees
.sp
The initial number of Huffman trees\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
After join
.sp
The number of distinct Huffman trees left after joining trees to save some header space\&.
.RE
.PP
After a table has been compressed, the
Field
lines displayed by
\fBmyisamchk \-dvv\fR
include additional information about each column:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Type
.sp
The data type\&. The value may contain any of the following descriptors:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
constant
.sp
All rows have the same value\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
no endspace
.sp
Do not store endspace\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
no endspace, not_always
.sp
Do not store endspace and do not do endspace compression for all values\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
no endspace, no empty
.sp
Do not store endspace\&. Do not store empty values\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
table\-lookup
.sp
The column was converted to an
ENUM\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
zerofill(\fIN\fR)
.sp
The most significant
\fIN\fR
bytes in the value are always 0 and are not stored\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
no zeros
.sp
Do not store zeros\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
always zero
.sp
Zero values are stored using one bit\&.
.RE
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Huff tree
.sp
The number of the Huffman tree associated with the column\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Bits
.sp
The number of bits used in the Huffman tree\&.
.RE
.PP
After you run
\fBmyisampack\fR, use
\fBmyisamchk\fR
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:
.sp
.if n \{\
.RS 4
.\}
.nf
myisamchk \-rq \-\-sort\-index \-\-analyze \fItbl_name\fR\&.MYI
.fi
.if n \{\
.RE
.\}
.PP
After you have installed the packed table into the MySQL database directory, you should execute
\fBmysqladmin flush\-tables\fR
to force
\fBmysqld\fR
to start using the new table\&.
.PP
To unpack a packed table, use the
\fB\-\-unpack\fR
option to
\fBmyisamchk\fR\&.
.SH "COPYRIGHT"
.br
.PP
Copyright \(co 1997, 2021, Oracle and/or its affiliates.
.PP
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.
.PP
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.
.PP
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/.
.sp
.SH "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/.
.SH AUTHOR
Oracle Corporation (http://dev.mysql.com/).