MySQL when I can use HASH instead of BTREE

Question

Since MySQL uses BTREE by default when creating the index, is there some kind of instance when I can use HASH ? For example, if my table consists only of foreign keys, which are simply INT UNSIGNED . Is it a good improvement to override BTREE with HASH in this case?

Not sure if that matters, but I'm using InnoDB .

Answer 1

The HASH index type is only supported for the MEMORY storage engine (aka HEAP ).