MySQL Variables delay_key_write 数据库 参数变量解释及正确配置使用

本站中文解释

delay_key_write 参数表示用于指定在更新索引的时候是否延迟写入索引，默认选项是OFF，当有更新索引的数据变动时就立即将索引写入磁盘，此参数被设置为ON时会延迟索引的写入，即：在关闭服务器的时候才会将更新后的索引写入磁盘。

设置该参数的方法：
1. 使用MySQL客户端连接到MySQL服务器，选择要设置参数的数据库；
2. 执行如下SQL语句以设置 delay_key_write参数为ON：
SET GLOBAL delay_key_write = ON;
3. 设置成功即可。

官方英文解释

delay_key_write

This variable specifies how to use delayed key writes. It
applies only to MyISAM tables. Delayed key
writing causes key buffers not to be flushed between writes.
See also Section 15.2.1, “MyISAM Startup Options”.

This variable can have one of the following values to affect
handling of the DELAY_KEY_WRITE table
option that can be used in CREATE
TABLE statements.

Note

If you set this variable to ALL, you
should not use MyISAM tables from within
another program (such as another MySQL server or
myisamchk) when the tables are in use.
Doing so leads to index corruption.

If DELAY_KEY_WRITE is enabled for a table,
the key buffer is not flushed for the table on every index
update, but only when the table is closed. This speeds up
writes on keys a lot, but if you use this feature, you should
add automatic checking of all MyISAM tables
by starting the server with the
myisam_recover_options system
variable set (for example,
myisam_recover_options='BACKUP,FORCE').
See Section 5.1.7, “Server System Variables”, and
Section 15.2.1, “MyISAM Startup Options”.

If you start mysqld with
--skip-new,
delay_key_write is set to
OFF.

Warning

If you enable external locking with
--external-locking, there is
no protection against index corruption for tables that use
delayed key writes.