myisamchk实用程序获取有关数据库表的信息或检查、修复或优化它们
。myisamchk使用
MyISAM表（具有
用于存储数据和索引的文件的表）
.MYD。.MYI
您还可以使用CHECK TABLE
andREPAIR TABLE语句来检查和修复MyISAM表。请参阅
第 13.7.2.2 节，“CHECK TABLE 语句”和
第 13.7.2.5 节，“REPAIR TABLE 语句”。
不支持对分区表 使用myisamchk 。
最好在执行表修复操作之前对表进行备份；在某些情况下，该操作可能会导致数据丢失。可能的原因包括但不限于文件系统错误。
像这样调用myisamchk：
myisamchk [options] tbl_name ...options指定您希望
myisamchk执行
的操作。它们在以下部分中描述。您还可以通过调用myisamchk --help获取选项列表。
没有选项，myisamchk只是检查你的表作为默认操作。要获得更多信息或告诉myisamchk采取纠正措施，请按照以下讨论中所述指定选项。
tbl_name是要检查或修复的数据库表。如果
在数据库目录以外的地方
运行myisamchk ，则必须指定数据库目录的路径，因为myisamchk不知道数据库位于何处。事实上，myisamchk实际上并不关心您正在处理的文件是否位于数据库目录中。您可以将对应于数据库表的文件复制到其他某个位置，并在那里对它们执行恢复操作。
如果愿意，您可以在myisamchk命令行
上命名多个表。您也可以通过命名其索引文件（具有.MYI
后缀的文件）来指定表。这使您能够使用模式指定目录中的所有表*.MYI。例如，如果您在数据库目录中，您可以
MyISAM像这样检查该目录中的所有表：
myisamchk *.MYI如果您不在数据库目录中，则可以通过指定目录路径来检查那里的所有表：
myisamchk /path/to/database_dir/*.MYI您甚至可以通过指定带有 MySQL 数据目录路径的通配符来检查所有数据库中的所有表：
myisamchk /path/to/datadir/*/*.MYI
快速检查所有
MyISAM表的推荐方法是：
myisamchk --silent --fast /path/to/datadir/*/*.MYI
如果要检查所有MyISAM表并修复任何损坏的表，可以使用以下命令：
myisamchk --silent --force --fast --update-state \
--key_buffer_size=64M --myisam_sort_buffer_size=64M \
--read_buffer_size=1M --write_buffer_size=1M \
/path/to/datadir/*/*.MYI此命令假定您有超过 64MB 的可用空间。有关使用myisamchk分配内存的更多信息 ，请参阅 第 4.6.3.6 节，“myisamchk 内存使用”。
有关使用 myisamchk的其他信息，请参阅 第 7.6 节，“MyISAM 表维护和崩溃恢复”。
You must ensure that no other program is using the tables while you are running myisamchk. The most effective means of doing so is to shut down the MySQL server while running myisamchk, or to lock all tables that myisamchk is being used on.
Otherwise, when you run myisamchk, it may display the following error message:
warning: clients are using or haven't closed the table properly
This means that you are trying to check a table that has been
updated by another program (such as the
mysqld server) that hasn't yet closed the
file or that has died without closing the file properly, which
can sometimes lead to the corruption of one or more
MyISAM tables.
If mysqld is running, you must force it to
flush any table modifications that are still buffered in
memory by using FLUSH TABLES.
You should then ensure that no one is using the tables while
you are running myisamchk
However, the easiest way to avoid this problem is to use
CHECK TABLE instead of
myisamchk to check tables. See
Section 13.7.2.2, “CHECK TABLE Statement”.
myisamchk supports the following options,
which can be specified on the command line or in the
[myisamchk] group of an option file. For
information about option files used by MySQL programs, see
Section 4.2.2.2, “Using Option Files”.
Table 4.20 myisamchk Options
| Option Name | Description |
|---|---|
| --analyze | Analyze the distribution of key values |
| --backup | Make a backup of the .MYD file as file_name-time.BAK |
| --block-search | Find the record that a block at the given offset belongs to |
| --check | Check the table for errors |
| --check-only-changed | Check only tables that have changed since the last check |
| --correct-checksum | Correct the checksum information for the table |
| --data-file-length | Maximum length of the data file (when re-creating data file when it is full) |
| --debug | Write debugging log |
| --decode_bits | Decode_bits |
| --defaults-extra-file | Read named option file in addition to usual option files |
| --defaults-file | Read only named option file |
| --defaults-group-suffix | Option group suffix value |
| --description | Print some descriptive information about the table |
| --extend-check | Do very thorough table check or repair that tries to recover every possible row from the data file |
| --fast | Check only tables that haven't been closed properly |
| --force | Do a repair operation automatically if myisamchk finds any errors in the table |
| --force | Overwrite old temporary files. For use with the -r or -o option |
| --ft_max_word_len | Maximum word length for FULLTEXT indexes |
| --ft_min_word_len | Minimum word length for FULLTEXT indexes |
| --ft_stopword_file | Use stopwords from this file instead of built-in list |
| --HELP | Display help message and exit |
| --help | Display help message and exit |
| --information | Print informational statistics about the table that is checked |
| --key_buffer_size | Size of buffer used for index blocks for MyISAM tables |
| --keys-used | A bit-value that indicates which indexes to update |
| --max-record-length | Skip rows larger than the given length if myisamchk cannot allocate memory to hold them |
| --medium-check | Do a check that is faster than an --extend-check operation |
| --myisam_block_size | Block size to be used for MyISAM index pages |
| --myisam_sort_buffer_size | The buffer that is allocated when sorting the index when doing a REPAIR or when creating indexes with CREATE INDEX or ALTER TABLE |
| --no-defaults | Read no option files |
| --parallel-recover | Uses the same technique as -r and -n, but creates all the keys in parallel, using different threads (beta) |
| --print-defaults | Print default options |
| --quick | Achieve a faster repair by not modifying the data file |
| --read_buffer_size | Each thread that does a sequential scan allocates a buffer of this size for each table it scans |
| --read-only | Do not mark the table as checked |
| --recover | Do a repair that can fix almost any problem except unique keys that aren't unique |
| --safe-recover | Do a repair using an old recovery method that reads through all rows in order and updates all index trees based on the rows found |
| --set-auto-increment | Force AUTO_INCREMENT numbering for new records to start at the given value |
| --set-collation | Specify the collation to use for sorting table indexes |
| --silent | Silent mode |
| --sort_buffer_size | 在执行 REPAIR 或使用 CREATE INDEX 或 ALTER TABLE 创建索引时对索引进行排序时分配的缓冲区 |
| --排序索引 | 按高低顺序对索引树块进行排序 |
| --sort_key_blocks | 排序键块 |
| --排序记录 | 根据特定索引对记录进行排序 |
| --排序恢复 | 强制 myisamchk 使用排序来解析键，即使临时文件会非常大 |
| --stats_method | 指定 MyISAM 索引统计信息收集代码应如何处理 NULL |
| --tmpdir | 用于存放临时文件的目录 |
| --解包 | 解压一个用 myisampack 打包的表 |
| --更新状态 | 在 .MYI 文件中存储信息以指示表何时被检查以及表是否崩溃 |
| --冗长 | 详细模式 |
| - 版本 | 显示版本信息并退出 |
| --write_buffer_size | 写入缓冲区大小 |