MySQL myisamchk修复正在使用，无法访问数据表

Posted on December 31, 2009 by axl MyISAM是MySQL的预设storage engine. MyISAM table很容易烂掉(corrupted)。
此文章将教你如何检查/修复这些烂掉的MyISAM tables.

每次你在MySQL DB 制造一个 table，将会在档案系统上同时制造出*.frm、*.MYD，跟*.MYI等三种格式的档案。

*.frm = 用来储存资料表格式(file to store table format)
*.MYD(MyData) = 用来储存资料(file to store data)
*.MYI(MyIndex) =用来储存索引(file to store index)

如何检查DB?哪个table 需要修复：

用root 执行以下指令，假设要检查DB1下的各个table

代码如下	复制代码
#myisamchk /var/lib/mysql/DB1/*.MYI >> /tmp/myisamchk.log

萤幕输出中，如果发现以下字样，该资料表就应修复

myisamchk: error: Keypointers and record positions doesn’t match
MyISAM-table ‘/var/lib/mysql/DB1/news_post_comment.MYI’ is corrupted
Fix it using switch “-r” or “-o”
myisamchk: warning: 1 client is using or hasn’t closed the table properly
MyISAM-table ‘/var/lib/mysql/DB1/news_post.MYI’ is usable but should be fixed
myisamchk: warning: 1 client is using or hasn’t closed the table properly
MyISAM-table ‘/var/lib/mysql/DB1/news_post_push_log.MYI’ is usable but should be fixed

Redirect出来的档案中会显示更多资讯。如下

代码如下	复制代码
Checking MyISAM file: /var/lib/mysql/DB1/yam_bbauth.MYI Data records: 14 Deleted blocks: 0 - check file-size - check record delete-chain - check key delete-chain - check index reference - check data record references index: 1 - check record links

如何利用myisamchk修复烂掉的tables：

找出烂掉的table之后，用以下指令修复，

代码如下	复制代码
#myisamchk –r /var/lib/mysql/DB1/news_post_comment.MYI - recovering (with sort) MyISAM-table ‘/var/lib/mysql/DB1/news_post_comment.MYI Data records: 1 - Fixing index 1

如果table正被某个application使用，你可能会看到： clients are using or haven’t closed the table properly。
所以建议修复前将mysqld关掉或用FLUSH TABLES锁住TABLES，防止修复时有application对DB TABLE做更动。

如何让检查跟修复同时进行：

代码如下	复制代码
#myisamchk --silent --force --fast --update-state /var/lib/mysql/DB1/*.MYI myisamchk: MyISAM file /var/lib/mysql/DB1/groups.MYI myisamchk: warning: 1 client is using or hasn’t closed the table properly myisamchk: MyISAM file /var/lib/mysql/DB1/profiles.MYI myisamchk: warning: 1 client is using or hasn’t closed the table properly

options 的意义如下：
• s, –silent option: Prints only errors. You can use two -s to make myisamchk very silent.
• -f, –force option: Restart myisamchk automatically with repair option -r, if there are any errors in the table.
• -F, –fast option: Check only tables that haven’t been closed properly.
• -U –update-state option: Marks tables as crashed, when it finds any error.

修复时手动分配记忆体给庞大的DB

庞大的table，修复需要很长的时间。修复时可以手动增加记忆体参数。

代码如下	复制代码
# myisamchk --silent --force --fast --update-state --key_buffer_size=512M --sort_buffer_size=512M --read_buffer_size=4M --write_buffer_size=4M /var/lib/mysql/DB1/*.MYI

用myisamchk 获取table资讯

代码如下

复制代码

#myisamchk -dvv profiles.MYI
MyISAM file: profiles.MYI
Record format: Packed
Character set: latin1_swedish_ci (8)
File-version: 1
Creation time: 2007-08-16 18:46:59
Status: open,changed,analyzed,optimized keys,sorted index pages
Auto increment key: 1 Last value: 88
Data records: 88 Deleted blocks: 0
Datafile parts: 118 Deleted data: 0
Datafile pointer (bytes): 4 Keyfile pointer (bytes): 4
Datafile length: 6292 Keyfile length: 6144
Max datafile length: 4294967294 Max keyfile length: 4398046510079
Recordlength: 2124

table description:
Key Start Len Index Type Rec/key Root Blocksize
1 2 3 unique int24 1 1024 1024
2 5 765 unique char packed stripped 1 2048 4096

Field Start Length Nullpos Nullbit Type
1 1 1
2 2 3 no zeros
3 5 765 no endspace

最后一招

#myisamchk --help

MySQL 使用 myisamchk 修复 *.MYI 时, 出现下述讯息:

myisamchk: Disk is full writing '/tmp/ST3lJjsW' (Errcode: 28). Waiting for someone to free space... (Expect up to 60 secs delay for server to c ontinue after freeing disk space)

myisamchk: Retry in 60 secs. Message reprinted in 600 secs

解法1:

■由讯息可以知道, myisamchk 需要使用到 /tmp, /tmp 容量不够就会出现此讯息, 所以如果 /tmp 可以清出空间, 清出 /tmp 的空间就可以解决了.
但是如果 /tmp 本身切的就不够大, 可以使用下述解法.

解法2:

此解法取自: free disk space error using myisamchk

■myisamchk -rq --sort_buffer_size=256M --key_buffer_size=256M --read_buffer_size=32M --write_buffer_size=32M --sort-index --analyze --tmpdir=/more-disk-space-directory/ /var/lib/mysql/database/T1.MYI
■?: 修改 --tmpdir=/more-disk-space-directory/ 指定到空间比较大的地方去即可.

补充：数据库,mysql教程