"David Monarchi" <david.e.monarchi@gmail.com> writes:
> I believe (but don't know) that a hash index would be better for this than a
> btree.
A fairly reliable rule of thumb is that there isn't *any* situation
where a Postgres hash index outperforms a btree.
Why this is so is not entirely clear, and various people keep poking
at the code in hopes of making it better. Sooner or later we'll either
succeed in getting hash indexes to be a win for specific use cases,
or give up and drop them entirely.
But at present it is undeniable that Postgres hash indexes are not
production quality. (Even if they had a performance win, their
current lack of WAL backup makes them unfit for production use...)
regards, tom lane