Robert Haas <robertmhaas@gmail.com> writes:
> As far as I know, exclusion constraints would work with hash opclasses
> also.
Yeah, they do.
> Do you think there's an advantage to having something that is
> hash-specific a la the btree-specific stuff we already have?
Sure: it'll be more efficient because of not needing an AFTER trigger.
Now of course this assumes that hash indexes ever grow up enough to play
in the big leagues, which is a pretty dubious proposition; but having
real unique-constraint support is one of the things people would want
from them if they ever did get to be credible production choices.
So this isn't something I'd put at the front of the TODO list for hash
indexes, but it ought to be in there somewhere.
regards, tom lane