1MYISAMPACK(1)               MariaDB Database System              MYISAMPACK(1)
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NAME

6       myisampack - generate compressed, read-only MyISAM tables
7

SYNOPSIS

9       myisampack [options] file_name ...
10

DESCRIPTION

12       The myisampack utility compresses MyISAM tables.  myisampack works by
13       compressing each column in the table separately. Usually, myisampack
14       packs the data file 40%–70%.
15
16       When the table is used later, the server reads into memory the
17       information needed to decompress columns. This results in much better
18       performance when accessing individual rows, because you only have to
19       uncompress exactly one row.
20
21       MySQL uses mmap() when possible to perform memory mapping on compressed
22       tables. If mmap() does not work, MySQL falls back to normal read/write
23       file operations.
24
25       Please note the following:
26
27       •   If the mysqld server was invoked with external locking disabled, it
28           is not a good idea to invoke myisampack if the table might be
29           updated by the server during the packing process. It is safest to
30           compress tables with the server stopped.
31
32       •   After packing a table, it becomes read only. This is generally
33           intended (such as when accessing packed tables on a CD).
34
35       Invoke myisampack like this:
36
37           shell> myisampack [options] file_name ...
38
39       Each file name argument should be the name of an index (.MYI) file. If
40       you are not in the database directory, you should specify the path name
41       to the file. It is permissible to omit the .MYI extension.
42
43       After you compress a table with myisampack, you should use myisamchk
44       -rq to rebuild its indexes.  myisamchk(1).
45
46       myisampack supports the following options. It also reads option files
47       and supports the options for processing them described at
48       Section 4.2.3.3.1, “Command-Line Options that Affect Option-File
49       Handling”.
50
51--help, -?
52
53           Display a help message and exit.
54
55--backup, -b
56
57           Make a backup of each table´s data file using the name
58           tbl_name.OLD.
59
60--character-sets-dir=path
61
62           The directory where character sets are installed. See Section 9.5,
63           “Character Set Configuration”.
64
65--debug[=debug_options], -# [debug_options]
66
67           Write a debugging log. A typical debug_options string is
68           ´d:t:o,file_name´. The default is ´d:t:o´.
69
70--force, -f
71
72           Produce a packed table even if it becomes larger than the original
73           or if the intermediate file from an earlier invocation of
74           myisampack exists. (myisampack creates an intermediate file named
75           tbl_name.TMD in the database directory while it compresses the
76           table. If you kill myisampack, the .TMD file might not be deleted.)
77           Normally, myisampack exits with an error if it finds that
78           tbl_name.TMD exists. With --force, myisampack packs the table
79           anyway.
80
81--join=big_tbl_name, -j big_tbl_name
82
83           Join all tables named on the command line into a single packed
84           table big_tbl_name. All tables that are to be combined must have
85           identical structure (same column names and types, same indexes, and
86           so forth).
87
88           big_tbl_name must not exist prior to the join operation. All source
89           tables named on the command line to be merged into big_tbl_name
90           must exist. The source tables are read for the join operation but
91           not modified. The join operation does not create a .frm file for
92           big_tbl_name, so after the join operation finishes, copy the .frm
93           file from one of the source tables and name it big_tbl_name.frm.
94
95--silent, -s
96
97           Silent mode. Write output only when errors occur.
98
99--test, -t
100
101           Do not actually pack the table, just test packing it.
102
103--tmpdir=path, -T path
104
105           Use the named directory as the location where myisampack creates
106           temporary files.
107
108--verbose, -v
109
110           Verbose mode. Write information about the progress of the packing
111           operation and its result.
112
113--version, -V
114
115           Display version information and exit.
116
117--wait, -w
118
119           Wait and retry if the table is in use. If the mysqld server was
120           invoked with external locking disabled, it is not a good idea to
121           invoke myisampack if the table might be updated by the server
122           during the packing process.
123
124       The following sequence of commands illustrates a typical table
125       compression session:
126
127           shell> ls -l station.*
128           -rw-rw-r--   1 monty    my         994128 Apr 17 19:00 station.MYD
129           -rw-rw-r--   1 monty    my          53248 Apr 17 19:00 station.MYI
130           -rw-rw-r--   1 monty    my           5767 Apr 17 19:00 station.frm
131           shell> myisamchk -dvv station
132           MyISAM file:     station
133           Isam-version:  2
134           Creation time: 1996-03-13 10:08:58
135           Recover time:  1997-02-02  3:06:43
136           Data records:              1192  Deleted blocks:              0
137           Datafile parts:            1192  Deleted data:                0
138           Datafile pointer (bytes):     2  Keyfile pointer (bytes):     2
139           Max datafile length:   54657023  Max keyfile length:   33554431
140           Recordlength:               834
141           Record format: Fixed length
142           table description:
143           Key Start Len Index   Type                 Root  Blocksize    Rec/key
144           1   2     4   unique  unsigned long        1024       1024          1
145           2   32    30  multip. text                10240       1024          1
146           Field Start Length Type
147           1     1     1
148           2     2     4
149           3     6     4
150           4     10    1
151           5     11    20
152           6     31    1
153           7     32    30
154           8     62    35
155           9     97    35
156           10    132   35
157           11    167   4
158           12    171   16
159           13    187   35
160           14    222   4
161           15    226   16
162           16    242   20
163           17    262   20
164           18    282   20
165           19    302   30
166           20    332   4
167           21    336   4
168           22    340   1
169           23    341   8
170           24    349   8
171           25    357   8
172           26    365   2
173           27    367   2
174           28    369   4
175           29    373   4
176           30    377   1
177           31    378   2
178           32    380   8
179           33    388   4
180           34    392   4
181           35    396   4
182           36    400   4
183           37    404   1
184           38    405   4
185           39    409   4
186           40    413   4
187           41    417   4
188           42    421   4
189           43    425   4
190           44    429   20
191           45    449   30
192           46    479   1
193           47    480   1
194           48    481   79
195           49    560   79
196           50    639   79
197           51    718   79
198           52    797   8
199           53    805   1
200           54    806   1
201           55    807   20
202           56    827   4
203           57    831   4
204           shell> myisampack station.MYI
205           Compressing station.MYI: (1192 records)
206           - Calculating statistics
207           normal:     20  empty-space:   16  empty-zero:     12  empty-fill:  11
208           pre-space:   0  end-space:     12  table-lookups:   5  zero:         7
209           Original trees:  57  After join: 17
210           - Compressing file
211           87.14%
212           Remember to run myisamchk -rq on compressed tables
213           shell> ls -l station.*
214           -rw-rw-r--   1 monty    my         127874 Apr 17 19:00 station.MYD
215           -rw-rw-r--   1 monty    my          55296 Apr 17 19:04 station.MYI
216           -rw-rw-r--   1 monty    my           5767 Apr 17 19:00 station.frm
217           shell> myisamchk -dvv station
218           MyISAM file:     station
219           Isam-version:  2
220           Creation time: 1996-03-13 10:08:58
221           Recover time:  1997-04-17 19:04:26
222           Data records:               1192  Deleted blocks:              0
223           Datafile parts:             1192  Deleted data:                0
224           Datafile pointer (bytes):      3  Keyfile pointer (bytes):     1
225           Max datafile length:    16777215  Max keyfile length:     131071
226           Recordlength:                834
227           Record format: Compressed
228           table description:
229           Key Start Len Index   Type                 Root  Blocksize    Rec/key
230           1   2     4   unique  unsigned long       10240       1024          1
231           2   32    30  multip. text                54272       1024          1
232           Field Start Length Type                         Huff tree  Bits
233           1     1     1      constant                             1     0
234           2     2     4      zerofill(1)                          2     9
235           3     6     4      no zeros, zerofill(1)                2     9
236           4     10    1                                           3     9
237           5     11    20     table-lookup                         4     0
238           6     31    1                                           3     9
239           7     32    30     no endspace, not_always              5     9
240           8     62    35     no endspace, not_always, no empty    6     9
241           9     97    35     no empty                             7     9
242           10    132   35     no endspace, not_always, no empty    6     9
243           11    167   4      zerofill(1)                          2     9
244           12    171   16     no endspace, not_always, no empty    5     9
245           13    187   35     no endspace, not_always, no empty    6     9
246           14    222   4      zerofill(1)                          2     9
247           15    226   16     no endspace, not_always, no empty    5     9
248           16    242   20     no endspace, not_always              8     9
249           17    262   20     no endspace, no empty                8     9
250           18    282   20     no endspace, no empty                5     9
251           19    302   30     no endspace, no empty                6     9
252           20    332   4      always zero                          2     9
253           21    336   4      always zero                          2     9
254           22    340   1                                           3     9
255           23    341   8      table-lookup                         9     0
256           24    349   8      table-lookup                        10     0
257           25    357   8      always zero                          2     9
258           26    365   2                                           2     9
259           27    367   2      no zeros, zerofill(1)                2     9
260           28    369   4      no zeros, zerofill(1)                2     9
261           29    373   4      table-lookup                        11     0
262           30    377   1                                           3     9
263           31    378   2      no zeros, zerofill(1)                2     9
264           32    380   8      no zeros                             2     9
265           33    388   4      always zero                          2     9
266           34    392   4      table-lookup                        12     0
267           35    396   4      no zeros, zerofill(1)               13     9
268           36    400   4      no zeros, zerofill(1)                2     9
269           37    404   1                                           2     9
270           38    405   4      no zeros                             2     9
271           39    409   4      always zero                          2     9
272           40    413   4      no zeros                             2     9
273           41    417   4      always zero                          2     9
274           42    421   4      no zeros                             2     9
275           43    425   4      always zero                          2     9
276           44    429   20     no empty                             3     9
277           45    449   30     no empty                             3     9
278           46    479   1                                          14     4
279           47    480   1                                          14     4
280           48    481   79     no endspace, no empty               15     9
281           49    560   79     no empty                             2     9
282           50    639   79     no empty                             2     9
283           51    718   79     no endspace                         16     9
284           52    797   8      no empty                             2     9
285           53    805   1                                          17     1
286           54    806   1                                           3     9
287           55    807   20     no empty                             3     9
288           56    827   4      no zeros, zerofill(2)                2     9
289           57    831   4      no zeros, zerofill(1)                2     9
290
291       myisampack displays the following kinds of information:
292
293       •   normal
294
295           The number of columns for which no extra packing is used.
296
297       •   empty-space
298
299           The number of columns containing values that are only spaces. These
300           occupy one bit.
301
302       •   empty-zero
303
304           The number of columns containing values that are only binary zeros.
305           These occupy one bit.
306
307       •   empty-fill
308
309           The number of integer columns that do not occupy the full byte
310           range of their type. These are changed to a smaller type. For
311           example, a BIGINT column (eight bytes) can be stored as a TINYINT
312           column (one byte) if all its values are in the range from -128 to
313           127.
314
315       •   pre-space
316
317           The number of decimal columns that are stored with leading spaces.
318           In this case, each value contains a count for the number of leading
319           spaces.
320
321       •   end-space
322
323           The number of columns that have a lot of trailing spaces. In this
324           case, each value contains a count for the number of trailing
325           spaces.
326
327       •   table-lookup
328
329           The column had only a small number of different values, which were
330           converted to an ENUM before Huffman compression.
331
332       •   zero
333
334           The number of columns for which all values are zero.
335
336       •   Original trees
337
338           The initial number of Huffman trees.
339
340       •   After join
341
342           The number of distinct Huffman trees left after joining trees to
343           save some header space.
344
345       After a table has been compressed, the Field lines displayed by
346       myisamchk -dvv include additional information about each column:
347
348       •   Type
349
350           The data type. The value may contain any of the following
351           descriptors:
352
353           •   constant
354
355               All rows have the same value.
356
357           •   no endspace
358
359               Do not store endspace.
360
361           •   no endspace, not_always
362
363               Do not store endspace and do not do endspace compression for
364               all values.
365
366           •   no endspace, no empty
367
368               Do not store endspace. Do not store empty values.
369
370           •   table-lookup
371
372               The column was converted to an ENUM.
373
374           •   zerofill(N)
375
376               The most significant N bytes in the value are always 0 and are
377               not stored.
378
379           •   no zeros
380
381               Do not store zeros.
382
383           •   always zero
384
385               Zero values are stored using one bit.
386
387       •   Huff tree
388
389           The number of the Huffman tree associated with the column.
390
391       •   Bits
392
393           The number of bits used in the Huffman tree.
394
395       After you run myisampack, you must run myisamchk to re-create any
396       indexes. At this time, you can also sort the index blocks and create
397       statistics needed for the MySQL optimizer to work more efficiently:
398
399           shell> myisamchk -rq --sort-index --analyze tbl_name.MYI
400
401       After you have installed the packed table into the MySQL database
402       directory, you should execute mysqladmin flush-tables to force mysqld
403       to start using the new table.
404
405       To unpack a packed table, use the --unpack option to myisamchk.
406
408       Copyright 2007-2008 MySQL AB, 2008-2010 Sun Microsystems, Inc.,
409       2010-2019 MariaDB Foundation
410
411       This documentation is free software; you can redistribute it and/or
412       modify it only under the terms of the GNU General Public License as
413       published by the Free Software Foundation; version 2 of the License.
414
415       This documentation is distributed in the hope that it will be useful,
416       but WITHOUT ANY WARRANTY; without even the implied warranty of
417       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
418       General Public License for more details.
419
420       You should have received a copy of the GNU General Public License along
421       with the program; if not, write to the Free Software Foundation, Inc.,
422       51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA or see
423       http://www.gnu.org/licenses/.
424
425

SEE ALSO

427       For more information, please refer to the MariaDB Knowledge Base,
428       available online at https://mariadb.com/kb/
429

AUTHOR

431       MariaDB Foundation (http://www.mariadb.org/).
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435MariaDB 10.5                     27 June 2019                    MYISAMPACK(1)
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