Does MyISAM load all indexes into memory?

First of all you should already 开发者_Go百科know MyISAM index doesn't include the actually data, it only has the address of data.

Reconsider my question if you don't know above before.

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myisam uses a cache only for keys - http://dev.mysql.com/doc/refman/5.5/en/myisam-key-cache.html - but for innodb keys and data are apparently treated equally - http://dev.mysql.com/doc/refman/5.5/en/innodb-buffer-pool.html

in both cases, the amount of information cached depends on the space available. if there is insufficient space then not all information is cached.

so, no, not always.