The myisampack utility compresses myisampack实用程序压缩MyISAM tables. myisampack works by compressing each column in the table separately. MyISAM表。myisampack通过分别压缩表中的每一列来工作。Usually, myisampack packs the data file 40% to 70%.通常，myisampack会将数据文件打包40%到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.稍后使用该表时，服务器会将解压缩列所需的信息读入内存。这会在访问单个行时带来更好的性能，因为您只需要解压缩一行。
MySQL uses MySQL在可能的情况下使用mmap() when possible to perform memory mapping on compressed tables. If mmap() does not work, MySQL falls back to normal read/write file operations.mmap()对压缩表执行内存映射。如果mmap()不起作用，MySQL将恢复正常的读/写文件操作。
Please note the following:请注意以下事项：
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. 如果mysqld服务器在禁用外部锁定的情况下被调用，如果服务器在打包过程中可能会更新表，则调用myisampack不是一个好主意。It is safest to compress tables with the server stopped.在服务器停止的情况下压缩表是最安全的。
After packing a table, it becomes read only. This is generally intended (such as when accessing packed tables on a CD).打包一张表后，它就变成了只读的。这通常是有意的（例如在访问CD上的打包表时）。
myisampack does not support partitioned tables.myisampack不支持分区表。
Invoke myisampack like this:像这样调用myisampack：
myisampack [options]file_name...
Each file name argument should be the name of an index (每个文件名参数都应该是索引（.MYI) file. .MYI）文件的名称。If you are not in the database directory, you should specify the path name to the file. It is permissible to omit the 如果不在数据库目录中，则应指定文件的路径名。允许省略.MYI extension..MYI扩展。
After you compress a table with myisampack, use myisamchk -rq to rebuild its indexes. Section 4.6.4, “myisamchk — MyISAM Table-Maintenance Utility”.使用myisampack压缩表后，使用myisamchk -rq重建其索引。第4.6.4节，“myisamck-MyISAM表维护实用程序”。
myisampack supports the following options. It also reads option files and supports the options for processing them described at Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.myisampack支持以下选项。它还读取选项文件，并支持第4.2.2.3节，“影响选项文件处理的命令行选项”中描述的处理选项。
--help, -?
Display a help message and exit.显示帮助消息并退出。
--backup, -b
Make a backup of each table's data file using the name 使用tbl_name.OLDtbl_name.OLD名称备份每个表的数据文件。
The directory where character sets are installed. See Section 10.15, “Character Set Configuration”.安装字符集的目录。参阅第10.15节，“字符集配置”。
--debug[=, debug_options]-# [debug_options]
Write a debugging log. A typical 编写调试日志。典型的debug_options string is d:t:o,. The default is file_named:t:o.debug_options字符串是d:t:o,file_name。默认值为d:t:o。
This option is available only if MySQL was built using 仅当MySQL使用WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option.WITH_DEBUG构建时，此选项才可用。Oracle提供的MySQL发布二进制文件不是使用此选项构建的。
--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. 即使打包表变得比原始表大，或者存在早期调用myisampack的中间文件，也要生成打包表。(myisampack creates an intermediate file named （myisampack在压缩表时在数据库目录中创建了一个名为tbl_name.TMDtbl_name.TMD的中间文件。If you kill myisampack, the 如果你杀死myisampack，.TMD file might not be deleted.) .TMD文件可能不会被删除。）Normally, myisampack exits with an error if it finds that 通常，如果myisampack发现tbl_name.TMDtbl_name.TMD存在，它会退出并返回错误。With 用--force, myisampack packs the table anyway.--force，myisampack无论如何都会收拾表。
--join=, big_tbl_name-j big_tbl_name
Join all tables named on the command line into a single packed table 将命令行上命名的所有表连接到一个打包表big_tbl_name.big_tbl_name中。 All tables that are to be combined must have identical structure (same column names and types, same indexes, and so forth).所有要组合的表必须具有相同的结构（相同的列名和类型、相同的索引等）。
big_tbl_name must not exist prior to the join operation. big_tbl_name不能存在。All source tables named on the command line to be merged into 要合并到big_tbl_name must exist. The source tables are read for the join operation but not modified.big_tbl_name中的命令行上命名的所有源表都必须存在。将为联接操作读取源表，但不会对其进行修改。
--silent, -s
Silent mode. Write output only when errors occur.静音模式。仅在出现错误时写入输出。
--test, -t
Do not actually pack the table, just test packing it.不要实际包装表，只需测试包装即可。
--tmpdir=, dir_name-T dir_name
Use the named directory as the location where myisampack creates temporary files.将命名目录用作myisampack创建临时文件的位置。
--verbose, -v
Verbose mode. Write information about the progress of the packing operation and its result.详细模式。写下有关包装操作进度及其结果的信息。
--version, -V
Display version information and exit.显示版本信息并退出。
--wait, -w
Wait and retry if the table is in use. 如果表正在使用中，请等待并重试。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.如果mysqld服务器在禁用外部锁定的情况下被调用，如果服务器在打包过程中可能会更新表，则调用myisampack不是一个好主意。
The following sequence of commands illustrates a typical table compression session:以下命令序列说明了典型的表压缩会话：
shell>ls -l station.*-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 shell>myisamchk -dvv stationMyISAM 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.MYICompressing 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-tablesshell>ls -l station.*-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 shell>myisamchk -dvv stationMyISAM 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:myisampack显示以下类型的信息：
normal
The number of columns for which no extra packing is used.不使用额外填料的列数。
empty-space
The number of columns containing values that are only spaces. These occupy one bit.包含仅为空格的值的列数。这些占据了一点。
empty-zero
The number of columns containing values that are only binary zeros. These occupy one bit.包含仅为二进制零的值的列数。这些占据了一点。
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. 不占用其类型的完整字节范围的整数列的数量。这些已更改为较小的类型。For example, a 例如，如果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.BIGINT列（八个字节）的所有值都在-128到127的范围内，则可以将其存储为TINYINT列（一个字节）。
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.用前导空格存储的十进制列数。在这种情况下，每个值都包含前导空格数的计数。
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.具有大量尾随空格的列数。在这种情况下，每个值都包含尾随空格数的计数。
table-lookup
The column had only a small number of different values, which were converted to an 该列只有少量不同的值，这些值在霍夫曼压缩之前被转换为ENUM before Huffman compression.ENUM。
zero
The number of columns for which all values are zero.所有值均为零的列数。
Original trees
The initial number of Huffman trees.霍夫曼树的初始数量。
After join
The number of distinct Huffman trees left after joining trees to save some header space.在连接树以节省一些标头空间后留下的不同霍夫曼树的数量。
After a table has been compressed, the 压缩表后，myisamchk -dvv显示的Field lines displayed by myisamchk -dvv include additional information about each column:field行包括有关每列的其他信息：
Type
The data type. The value may contain any of the following descriptors:数据类型。该值可以包含以下任何描述符：
constant
All rows have the same value.所有行都有相同的值。
no endspace
Do not store endspace.不要存储尾部空格。
no endspace, not_always
Do not store endspace and do not do endspace compression for all values.不要存储端隙，也不要对所有值进行端隙压缩。
no endspace, no empty
Do not store endspace. Do not store empty values.不要存储尾部空格。不要存储空值。
table-lookup
The column was converted to an 该列已转换为ENUM.ENUM。
zerofill(N)
The most significant 值中最重要的N bytes in the value are always 0 and are not stored.N个字节始终为0，不会被存储。
no zeros
Do not store zeros.不要存储零。
always zero
Zero values are stored using one bit.零值使用一位存储。
Huff tree
The number of the Huffman tree associated with the column.与该列关联的霍夫曼树的编号。
Bits
The number of bits used in the Huffman tree.霍夫曼树中使用的比特数。
After you run myisampack, use myisamchk to re-create any indexes. 运行myisampack后，使用myisamchk重新创建任何索引。At this time, you can also sort the index blocks and create statistics needed for the MySQL optimizer to work more efficiently:此时，您还可以对索引块进行排序，并创建MySQL优化器更有效地工作所需的统计数据：
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.将打包表安装到MySQL数据库目录后，应执行mysqladmin flush tables以强制mysqld开始使用新表。
To unpack a packed table, use the 要打开打包好的表，请使用myisamchk的--unpack option to myisamchk.--unpack选项。