Robert Haas <robertmhaas@gmail.com> writes:
> I thought the theoretical advantage of hash indexes wasn't that they
> were smaller but that you avoided a central contention point (the
> btree root).
> Of course our current hash indexes have *more* not less contention
> than btree but I'm pretty comfortable chalking that up to quality of
> implementation rather than anything intrinsic.
The long and the short of it is that there are *lots* of implementation
deficiences in our hash indexes. There's no real way to know whether
they'd be competitive if all those things were rectified, except by doing
the work to fix 'em. And it's hard to justify putting much effort into
hash indexes so long as there's an elephant in the room of the size of "no
WAL support". So I'm in favor of getting that fixed, if we have somebody
who's willing to do it. It might lead to good things later; and even if
it doesn't, the lack of WAL support is an embarrassment.
regards, tom lane