Yeah. This wasn't the case a while back--PostgreSQL was missing support for what I think people call covered indexes, and so would only use the index to filter

Yeah. This wasn't the case a while back--PostgreSQL was missing support for what I think people call covered indexes, and so would only use the index to filter a set of candidate rows and then still had to go digging around in the real tuple to verify it matched--but I am pretty sure they changed that a while back.