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@momjian.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@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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