Chapman Flack <chap@anastigmatix.net> writes:
> Was my guess about the reason right? Does this PG10 announcement
> also mean it will be possible to use UNIQUE constraints with some
> pure-identifier, no-natural-ordering type that supports only hashing?
No, nobody's done anything about allowing hash indexes to support
uniqueness AFAIK. I don't have a clear picture of how much work
it would be, but it would likely be more than trivial effort;
there's definitely extra code in btree that supports that.
(You might be right about the big picture, in that no one wanted to
bother with working on that as long as hash indexes weren't crash
safe. But there's not a technical connection.)
regards, tom lane