Re: SELECT from a set of values really slow?

Tim Smith <reply_in_group@mouse-potato.com> writes:
>     SELECT id FROM bench WHERE data IN ('X', 'Y')

> To my surprise, when I tried this trick with PostgreSQL, it did not
> speed things up.  In fact, it *massively* slowed down--it only is
> getting 13 selects in 3 seconds, searching for two at a time.

> What's going on here?

Likely it's switching from index to sequential scan because of a poor
estimate of how many rows will be returned.  Have you ever ANALYZEd
the test table?  Without either ANALYZE stats or a unique index,
the planner will certainly not think that the column is unique.

            regards, tom lane