Re: GSoC on WAL-logging hash indexes

On Wed, Apr 30, 2014 at 10:11 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> 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).

The B-Tree root isn't really a central contention point at all. The
locking/latching protocol that nbtree uses is remarkably
concurrency-friendly. In the real world, there is pretty much no
exclusive locking of the root page's buffer.

> 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.

I am not convinced of that.

--
Peter Geoghegan