'\" t
.\"     Title: \fBmyisampack\fR
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 01/04/2021
.\"    Manual: MySQL Database System
.\"    Source: MySQL 5.6
.\"  Language: English
.\"
.TH "\FBMYISAMPACK\FR" "1" "01/04/2021" "MySQL 5\&.6" "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
shell> \fBmyisampack [\fR\fB\fIoptions\fR\fR\fB] \fR\fB\fIfile_name\fR\fR\fB \&.\&.\&.\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\&.
\fBmyisamchk\fR(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
shell> \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
shell> \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
shell> \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
shell> \fBmyisamchk \-rq station\fR
\- check record delete\-chain
\- recovering (with sort) MyISAM\-table \*(Aqstation\*(Aq
Data records: 1192
\- Fixing index 1
\- Fixing index 2
shell> \fBmysqladmin \-uroot flush\-tables\fR
shell> \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
shell> \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
shell> \fBmyisamchk \-rq \-\-sort\-index \-\-analyze \fR\fB\fItbl_name\fR\fR\fB\&.MYI\fR
.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/).
