要调查数据库页损坏，你可以使用 SELECT ... INTO OUTFILE 从数据库导出你的表。通常，通过这种方式获得的大多数数据都是完整的。严重的损坏可能会导致 SELECT * FROM tbl_name 语句或 InnoDB 后台操作意外退出或断言，甚至可能导致 InnoDB 前滚恢复崩溃。在这种情况下，你可以使用 innodb_force_recovery 选项来强制 InnoDB 存储引擎启动，同时阻止后台操作运行，以便你可以导出表。例如，你可以在重启服务器前，将以下行添加到选项文件的 [mysqld] 部分：To investigate database page corruption, you might dump your tables from the database with SELECT ... INTO OUTFILE. Usually, most of the data obtained in this way is intact. Serious corruption might cause SELECT * FROM tbl_name statements or InnoDB background operations to unexpectedly exit or assert, or even cause InnoDB roll-forward recovery to crash. In such cases, you can use the innodb_force_recovery option to force the InnoDB storage engine to start up while preventing background operations from running, so that you can dump your tables. For example, you can add the following line to the [mysqld] section of your option file before restarting the server:

[mysqld]
innodb_force_recovery = 1

有关使用选项文件的信息，请参见第 6.2.2.2 节，“使用选项文件”。For information about using option files, see Section 6.2.2.2, “Using Option Files”.

innodb_force_recovery 默认值为 0（正常启动，不进行强制恢复）。innodb_force_recovery 可接受的非零值为 1 到 6。较大的值包含较小值的功能。例如，值为 3 包含值 1 和 2 的所有功能。innodb_force_recovery is 0 by default (normal startup without forced recovery). The permissible nonzero values for innodb_force_recovery are 1 to 6. A larger value includes the functionality of lesser values. For example, a value of 3 includes all of the functionality of values 1 and 2.

如果你能够在 innodb_force_recovery 值为 3 或以下的情况下导出你的表，那么你相对安全，只会丢失一些损坏的单个页面上的数据。值为 4 或更高被认为是危险的，因为数据文件可能会被永久损坏。值为 6 被认为是极端的，因为数据库页面会处于过时状态，这反过来可能会导致 B 树 和其他数据库结构中出现更多的损坏。If you are able to dump your tables with an innodb_force_recovery value of 3 or less, then you are relatively safe that only some data on corrupt individual pages is lost. A value of 4 or greater is considered dangerous because data files can be permanently corrupted. A value of 6 is considered drastic because database pages are left in an obsolete state, which in turn may introduce more corruption into B-trees and other database structures.

作为一种安全措施，当 innodb_force_recovery 大于 0 时，InnoDB 会阻止 INSERT、UPDATE 或 DELETE 操作。innodb_force_recovery 设置为 4 或更高将使 InnoDB 进入只读模式。As a safety measure, InnoDB prevents INSERT, UPDATE, or DELETE operations when innodb_force_recovery is greater than 0. An innodb_force_recovery setting of 4 or greater places InnoDB in read-only mode.

你可以从表中 SELECT 出数据。 当 innodb_force_recovery 值为 3 或更低时，你可以 DROP 或 CREATE 表。 使用大于 3 的 innodb_force_recovery 值也支持 DROP TABLE。 当 innodb_force_recovery 值大于 4 时，不允许 DROP TABLE。You can SELECT from tables to dump them. With an innodb_force_recovery value of 3 or less you can DROP or CREATE tables. DROP TABLE is also supported with an innodb_force_recovery value greater than 3. DROP TABLE is not permitted with an innodb_force_recovery value greater than 4.

如果你知道某个表在回滚时导致意外退出，你可以删除它。如果遇到因失败的大量导入或 ALTER TABLE 引起的失控回滚，你可以终止 mysqld 进程，并将 innodb_force_recovery 设置为 3，以在不进行回滚的情况下启动数据库，然后 DROP 导致失控回滚的表。If you know that a given table is causing an unexpected exit on rollback, you can drop it. If you encounter a runaway rollback caused by a failing mass import or ALTER TABLE, you can kill the mysqld process and set innodb_force_recovery to 3 to bring the database up without the rollback, and then DROP the table that is causing the runaway rollback.

如果表数据中的损坏阻止你导出整个表的内容，带有 ORDER BY primary_key DESC 子句的查询可能能够导出损坏部分之后的表数据。If corruption within the table data prevents you from dumping the entire table contents, a query with an ORDER BY primary_key DESC clause might be able to dump the portion of the table after the corrupted part.

如果需要较高的 innodb_force_recovery 值来启动 InnoDB，可能存在损坏的数据结构，这可能导致复杂查询（包含 WHERE、ORDER BY 或其他子句的查询）失败。在这种情况下，你可能只能运行基本的 SELECT * FROM t 查询。If a high innodb_force_recovery value is required to start InnoDB, there may be corrupted data structures that could cause complex queries (queries containing WHERE, ORDER BY, or other clauses) to fail. In this case, you may only be able to run basic SELECT * FROM t queries.