can you use INDEX DIRECTORY= with ALTER TABLE/CREATE INDEX?

[Mark Modrall]

Hi...

I have a process that creates an index temporarily on a table, uses it for some calculation, and then drops it. Someone else in our company found that for small indexes (and temporary) indexes he could get huge performance gains putting the index in a ram disk.

When I went to try the technique in my program (on pre-existing tables), I tried to specify INDEX DIRECTORY= on the CREATE INDEX statement, but I keep getting a parse error. At least as I understand the bnf for the documentation, it looks like it should work, but I'm not getting much in the error message about what the parse doesn't like. Is it just impossible to mix INDEX DIRECTORY with CREATE INDEX or ALTER TABLE?

I've tried
CREATE INDEX itest on test (time) INDEX_DIRECTORY='/mnt/ramtmp'
ALTER TABLE test ADD INDEX itest (time) INDEX_DIRECTORY='/mnt/ramtmp'

and get parse errors on both.

I'm using MySql 4.1.16.

Thanks
_mark