问题
Since MySQL uses BTREE by default when creating an index, is there some instance when I can use HASH? For example, if my table only consists of Foreign Keys which are just INT UNSIGNED values. Is it a good improvement to override BTREE with HASH in this case?
Not sure if it matters, but I'm using InnoDB.
回答1:
The HASH index type is only supported for MEMORY (aka HEAP) storage engine.
来源：https://stackoverflow.com/questions/14418260/mysql-when-can-i-use-hash-instead-of-btree