Re: Hash partitioning.

On Tue, Jun 25, 2013 at 11:02:40AM -0400, Robert Haas wrote:
> On Tue, Jun 25, 2013 at 9:21 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > On Tue, Jun 25, 2013 at 03:48:19PM +0300, Yuri Levinsky wrote:
> >> Hi,
> >>
> >> Do we have any plans to implement Hash Partitioning, maybe I missing this
> >> feature?
> >
> > You can do it by writing your own constraint and trigger functions that
> > control the hashing.
>
> Not really. Constraint exclusion won't kick in for a constraint like
> CHECK (hashme(a) % 16 == 3) and a WHERE clause of the form a = 42.

Uh, I thought we checked the constant against every CHECK constraint and
only scanned partitions that matched. Why does this not work?

> Of course, since partitioning generally doesn't improve performance in
> PostgreSQL anyway, it's not clear why you'd want to do this in the

I think partitioning does improve performance by reducing index depth.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +