4.6.4.5 Obtaining Table Information with myisamchk用myisamchk获取表信息

To obtain a description of a MyISAM table or statistics about it, use the commands shown here. The output from these commands is explained later in this section.要获取MyISAM表的描述或有关它的统计信息，请使用此处显示的命令。本节稍后将解释这些命令的输出。

The tbl_name argument can be either the name of a MyISAM table or the name of its index file, as described in Section 4.6.4, “myisamchk — MyISAM Table-Maintenance Utility”. tbl_name参数可以是MyISAM表的名称，也可以是其索引文件的名称，如第4.6.4节，“myisamchk-MyISAM表维护实用程序”所述。Multiple tbl_name arguments can be given.可以给出多个tbl_name参数。

Suppose that a table named person has the following structure. 假设一个名为person的表具有以下结构。(The MAX_ROWS table option is included so that in the example output from myisamchk shown later, some values are smaller and fit the output format more easily.)（包含MAX_ROWS表选项，以便在稍后显示的myisamchk的示例输出中，一些值更小，更容易适应输出格式。）

CREATE TABLE person
(
  id         INT NOT NULL AUTO_INCREMENT,
  last_name  VARCHAR(20) NOT NULL,
  first_name VARCHAR(20) NOT NULL,
  birth      DATE,
  death      DATE,
  PRIMARY KEY (id),
  INDEX (last_name, first_name),
  INDEX (birth)
) MAX_ROWS = 1000000 ENGINE=MYISAM;

Suppose also that the table has these data and index file sizes:还假设该表具有以下数据和索引文件大小：

-rw-rw----  1 mysql  mysql  9347072 Aug 19 11:47 person.MYD
-rw-rw----  1 mysql  mysql  6066176 Aug 19 11:47 person.MYI

Example of myisamchk -dvv output:myisamchk -dvv输出示例：

MyISAM file:         person
Record format:       Packed
Character set:       utf8mb4_0900_ai_ci (255)
File-version:        1
Creation time:       2017-03-30 21:21:30
Status:              checked,analyzed,optimized keys,sorted index pages
Auto increment key:              1  Last value:                306688
Data records:               306688  Deleted blocks:                 0
Datafile parts:             306688  Deleted data:                   0
Datafile pointer (bytes):        4  Keyfile pointer (bytes):        3
Datafile length:           9347072  Keyfile length:           6066176
Max datafile length:    4294967294  Max keyfile length:   17179868159
Recordlength:                   54

table description:
Key Start Len Index   Type                     Rec/key         Root  Blocksize
1   2     4   unique  long                           1                    1024
2   6     80  multip. varchar prefix                 0                    1024
    87    80          varchar                        0
3   168   3   multip. uint24 NULL                    0                    1024

Field Start Length Nullpos Nullbit Type
1     1     1
2     2     4                      no zeros
3     6     81                     varchar
4     87    81                     varchar
5     168   3      1       1       no zeros
6     171   3      1       2       no zeros

Explanations for the types of information myisamchk produces are given here. 这里给出了myisamchk产生的信息类型的解释。“Keyfile” refers to the index file. “Record” and “row” are synonymous, as are “field” and “column.”“Keyfile”指的是索引文件。“记录”和“行”是同义词，“字段”和“列”也是同义词

The initial part of the table description contains these values:表描述的初始部分包含以下值：

The table description part of the output includes a list of all keys in the table. For each key, myisamchk displays some low-level information:输出的table description部分包括表中所有键的列表。对于每个键，myisamchk显示一些低级信息：

The last part of the output provides information about each column:输出的最后一部分提供了有关每一列的信息：

The Huff tree and Bits fields are displayed if the table has been compressed with myisampack. 如果表已使用myisampack压缩，则显示Huff树和Bits字段。See Section 4.6.6, “myisampack — Generate Compressed, Read-Only MyISAM Tables”, for an example of this information.有关此信息的示例，请参阅第4.6.6节，“myisampack——生成压缩的只读MyISAM表”。

Example of myisamchk -eiv output:myisamchk -eiv输出示例：

Checking MyISAM file: person
Data records:  306688   Deleted blocks:       0
- check file-size
- check record delete-chain
No recordlinks
- check key delete-chain
block_size 1024:
- check index reference
- check data record references index: 1
Key:  1:  Keyblocks used:  98%  Packed:    0%  Max levels:  3
- check data record references index: 2
Key:  2:  Keyblocks used:  99%  Packed:   97%  Max levels:  3
- check data record references index: 3
Key:  3:  Keyblocks used:  98%  Packed:  -14%  Max levels:  3
Total:    Keyblocks used:  98%  Packed:   89%

- check records and index references
*** LOTS OF ROW NUMBERS DELETED ***

Records:            306688  M.recordlength:       25  Packed:            83%
Recordspace used:       97% Empty space:           2% Blocks/Record:   1.00
Record blocks:      306688  Delete blocks:         0
Record data:       7934464  Deleted data:          0
Lost space:         256512  Linkdata:        1156096

User time 43.08, System time 1.68
Maximum resident set size 0, Integral resident set size 0
Non-physical pagefaults 0, Physical pagefaults 0, Swaps 0
Blocks in 0 out 7, Messages in 0 out 0, Signals 0
Voluntary context switches 0, Involuntary context switches 0
Maximum memory usage: 1046926 bytes (1023k)

myisamchk -eiv output includes the following information:myisamchk -eiv输出包括以下信息：