MySQL数据库中部分数据损坏快速恢复过

前几天因为SQL/Index.html">MySQL数据库部分数据损坏原因，我尝试了下恢复数据，之后整理以下文档，供各位参考，以备各位同事以后如有类似问题，可以少走些弯路，尽快解决问题。

环境：Windows2003
数据库：SQL/Index.html">MySQL
损坏数据文件名：function_products

将数据库内容物理文件直接导入到mysql\data下，每只表各3个文件，依次分别为：.frm .myd .myi。首先我第一想到的是去网上搜索，寻找类似的工具，试图通过工具来恢复已损坏的文件，于是我在google上查找，找到一款名为mysqlrecovery的工具，安装后我用其进行恢复，只可惜效果太不理想，几十MB大的数据文件，恢复之后它提示我竟然只有几十KB。我又想到了SQL/Index.html">MySQL下应有自己本身的修复程序等，于是想通过其来进行恢复，心想应不会太差劲吧，在网上查找了资料，提示：由于临时断电，使用kill -9中止SQL/Index.html">MySQL服务进程，或者是SQL/Index.html">MySQL正在高速运转时进行强制备份操作时等，所有的这些都可能会毁坏SQL/Index.html">MySQL的数据文件。如果在被干扰时，服务正在改变文件，文件可能会留下错误的或不一致的状态。因为这样的毁坏有时是不容易被发现的，当你发现这个错误时可能是很久以后的事了。

于是，当你发现这个问题时，也许所有的备份都有同样的错误。我想我现在碰到的问题可能是这个问题，因为备份的数据也是有部分损坏的数据，所以导致不能完全运行， 意识到myisamchk程序对用来检查和修改的SQL/Index.html">MySQL数据文件的访问应该是唯一的。如果SQL/Index.html">MySQL服务正在使用某一文件，并对myisamchk正在检查的文件进行修改，myisamchk会误以为发生了错误，并会试图进行修复--这将导致SQL/Index.html">MySQL服务的崩溃！这样，要避免这种情况的发生，通常我们需要在工作时关闭SQL/Index.html">MySQL服务。作为选择，你也可以暂时关闭服务以制作一个文件的拷贝，然后在这个拷贝上工作。当你做完了以后，重新关闭服务并使用新的文件取代原来的文件(也许你还需要使用期间的变更日志)。

SQL/Index.html">MySQL数据目录不是太难理解的。每一个数据库对应一个子目录，每个子目录中包含了对应于这个数据库中的数据表的文件。每一个数据表对应三个文件，它们和表名相同，但是具有不同的扩展名。tblname.frm文件是表的定义，它保存了表中包含的数据列的内容和类型。tblname.myd文件包含了表中的数据。tblname.myi文件包含了表的索引(例如，它可能包含lookup表以帮助提高对表的主键列的查询)。 要检查一个表的错误，只需要运行myisamchk(在SQL/Index.html">MySQL的bin目录下)并提供文件的位置和表名，或者是表的索引文件名：

% myisamchk /usr/local/mysql/var/dbname/tblname

% myisamchk /usr/local/mysql/var/dbname/tblname.myi

上面的两个命令都可以执行对指定表的检查。要检查数据库中所有的表，可以使用通配符：

% myisamchk /usr/local/mysql/var/dbname/*.myi

要检查所有数据库中的所有表，可以使用两个通配符：

% myisamchk /usr/local/mysql/var/*/*.myi

如果不带任何选项，myisamchk将对表文件执行普通的检查。如果你对一个表有怀疑，但是普通的检查不能发现任何错误，你可以执行更彻底的检查(但是也更慢！)，这需要使用--extend-check选项：

% myisamchk --extend-check /path/to/tblname

对错误的检查是没有破坏性的，这意味着你不必担心执行对你的数据文件的检查会使已经存在的问题变得更糟。另一方面，修复选项，虽然通常也是安全的，但是它对你的数据文件的更改是无法撤消的。因为这个原因，我们强烈推荐你试图修复一个被破坏的表文件时首先做个备份，并确保在制作这个备份之前你的SQL/Index.html">MySQL服务是关闭的。
我在Win2003下通过命令提示符，输入：

注：此为记录我当时操作的全部过程d:\documents and settings\administrator>c:c:\>cd SQL/Index.html">MySQLc:\mysql>cd datac:\mysql\data>cd hw_enterpricec:\mysql\data\hw_enterprice>myisamchk function_products.frm'myisamchk' 不是内部或外部命令，也不是可运行的程序或批处理文件。c:\mysql\data\hw_enterprice>cd\c:\>cd mysqlc:\mysql>cd bin注：查看myisamchk的帮助信息c:\mysql\bin>myisamchkmyisamchk ver 2.6 for win95/win98 at i32by monty, for your professional usethis software comes with no warranty: see the public for details.description, check and repair of isam tables.used without options all tables on the command will be checked for errorsusage: myisamchk [options] tables[.myi]global options:-#, --debug=...   output debug log. often this is 'd:t:o,filename'-?, --help       display this help and exit.-o, --set-variable var=optionchange the value of a variable. please note thatthis option is deprecated; you can set variablesdirectly with '--variable-name=value'.-t, --tmpdir=path   path for temporary files-s, --silent     only print errors. one can use two -s to makemyisamchk very silent-v, --verbose     print more information. this can be used with--description and --check. use many -v for more verbosity! -v, --version     print version and exit.-w, --wait       wait if table is locked.check options (check is the default action for myisamchk):-c, --check       check table for errors-e, --extend-check check the table very throughly. only use this inextreme cases as myisamchk should normally be able tofind out if the table is ok even without this switch-f, --fast       check only tables that haven't been closed properly-c, --check-only-changedcheck only tables that have changed since last check-f, --force       restart with '-r' if there are any errors in the table.states will be updated as with '--update-state'-i, --information   print statistics information about table that is checked-m, --medium-check faster than extend-check, but only finds 99.99% ofall errors. should be good enough for most cases-u --update-state mark tables as crashed if you find any errors-t, --read-only   don't mark table as checkedrepair options (when using '-r' or '-o')-b, --backup     make a backup of the .myd file as 'filename-time.bak'--correct-checksum correct checksum information for table.-d, --data-file-length=# max length of data file (when recreating datafile when it's full)-e, --extend-check try to recover every possible row from the data filenormally this will also find a lot of garbage rows;don't use this option if you are not totally desperate.-f, --force       overwrite old temporary files.-k, --keys-used=#   tell myisam to update only some specific keys. # is abit mask of which keys to use. this can be used toget faster inserts!-r, --recover     can fix almost anything except unique keys that aren'tunique.-n, --sort-recover forces recovering with sorting even if the temporaryfile would be very big.-p, --parallel-recoveruses the same technique as '-r' and '-n', but createsall the keys in parallel, in different threads.this is alpha code. use at your own risk!-o, --safe-recover uses old recovery method; slower than '-r' but canhandle a couple of cases where '-r' reports that itcan't fix the data file.--character-sets-dir=...directory where character sets are--set-character-set=namechange the character set used by the index-q, --quick       faster repair by not modifying the data file.one can give a second '-q' to force myisamchk tomodify the original datafile in case of duplicate keys-u, --unpack     unpack file packed with myisampack.other actions:-a, --analyze     analyze distribution of keys. will make some joins inSQL/Index.html">MySQL faster. you can check the calculated distributionby using '--description --verbose table_name'.-d, --description   prints some information about table.-a, --set-auto-increment[=value]force auto_increment to start at this or higher valueif no value is given, then sets the next auto_incrementvalue to the highest used value for the auto key + 1.-s, --sort-index   sort index blocks. this speeds up 'read-next' inapplications-r, --sort-records=#sort records according to an index. this makes yourdata much more localized and may speed up thingsc:\mysql\bin>myisamchk c:\mysql\data\hw_enterprice\function_products.frmmyisamchk: error: 'c:\mysql\data\hw_enterprice\function_products.frm' is not a myisam-tablec:\mysql\bin>myisamchk c:\mysql\data\hw_enterprice\function_products.myichecking myisam file: c:\mysql\data\hw_enterprice\function_products.myidata records:   85207   deleted blocks:     39myisamchk: warning: table is marked as crashedmyisamchk: warning: 1 clients is using or hasn't closed the table properly- check file-size- check key delete-chain- check record delete-chainmyisamchk: error: record delete-link-chain corrupted- check index reference- check data record references index: 1- check data record references index: 2- check data record references index: 3- check record linksmyisamchk: error: wrong bytesec: 0-195-171 at linkstart: 841908myisam-table 'c:\SQL/Index.html">MySQL\data\hw_enterprice\function_products.myi' is corruptedfix it using switch "-r" or "-o"

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