pack_isam is an extra that you get when ordering more than 10
licenses or extended support. Since pack_isam is distributed
binary only, pack_isam is only available on some platforms.
Of course, all future updates to pack_isam is included in the
price. pack_isam may at some time be included as standard when
we get some kind of turnover for MySQL.
pack_isam works by compressing each column in the table
separately. The information needed to decompress is read into memory
when the table is opened. This gives a much better performance when
accessing individual records as one only has to uncompress exactly one
record, not a much larger disk block like when using Stacker on MSDOS.
MySQL uses memory mapping (mmap) on compressed tables and falls back to normal read/write file usage if mmap doesn't work.
Usually, pack_isam packs the datafile 40-70%.
There is currently two limitations with pack_isam:
Fixing these limitations is on our TODO but with low priority.
pack_isam options:
> pack_isam --help
pack_isam Ver 5.0 for SOLARIS 2.5 on SPARCstation
Copyright (C) 1994-1997 TcX AB & Monty Program KB & Detron HB.
This is not free software. You must have a license to use this program
This software comes with ABSOLUTELY NO WARRANTY
Pack an ISAM-database to take much smaller space
Keys are not updated, one must run isamchk -rq on datafile afterwards
Usage: pack_isam [OPTIONS]
-b, --backup Make a backup of the table as table_name.OLD
-f, --force Force packing of table even if it's gets bigger or
tempfile exists.
-j, --join=# Join all given tables into table.
All tables MUST be identical.
-p, --packlength=# Force storage size of recordlength (1,2 or 3)
-s, --silent Be more silent.
-t, --test Don't pack table only test packing it
-v, --verbose Write info about progress and packing result
-w, --wait Wait and retry if table is in use
-T, --tmp_dir=# Use temporary directory to store temporary table
-#, --debug=... output debug log. Often this is 'd:t:o,filename`
-?, --help display this help and exit
-V, --version output version information and exit
Typical run:
(/my/monty/tmp) ls -l station.*
-rw-rw-r-- 1 monty my 994128 Apr 17 19:00 station.ISD
-rw-rw-r-- 1 monty my 53248 Apr 17 19:00 station.ISM
-rw-rw-r-- 1 monty my 5767 Apr 17 19:00 station.frm
(/my/monty/tmp) isamchk -dvv station
ISAM 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
Datafilepointer (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
column 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
Compressing station.ISD: (1192 records)
- Calculating statistics
normal: 20 empty-space: 16 empty-zero: 12 empty-fill: 11
pre-space: 0 end-space: 12 intervall-fields: 5 zero: 7
Original trees: 57 After join: 17
- Compressing file
87.14%
(/my/monty/tmp) ls -l station.*
-rw-rw-r-- 1 monty my 127874 Apr 17 19:00 station.ISD
-rw-rw-r-- 1 monty my 55296 Apr 17 19:04 station.ISM
-rw-rw-r-- 1 monty my 5767 Apr 17 19:00 station.frm
(my/monty/tmp) isamchk -dvv station
ISAM 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
Datafilepointer (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-lockup 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 allways zero 2 9
21 336 4 allways zero 2 9
22 340 1 3 9
23 341 8 table-lockup 9 0
24 349 8 table-lockup 10 0
25 357 8 allways 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-lockup 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 allways zero 2 9
34 392 4 table-lockup 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 allways zero 2 9
40 413 4 no zeros 2 9
41 417 4 allways zero 2 9
42 421 4 no zeros 2 9
43 425 4 allways 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
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