To: Josh Berkus <josh@agliodbs.com>
cc: pgsql-performance@postgresql.org
Subject: Re: Issue for partitioning with extra check constriants 
In-reply-to: <4CA672D7.3070405@agliodbs.com> 
References: <4CA672D7.3070405@agliodbs.com>
Comments: In-reply-to Josh Berkus <josh@agliodbs.com>
	message dated "Fri, 01 Oct 2010 16:46:31 -0700"
Date: Fri, 01 Oct 2010 19:56:17 -0400
Message-ID: <1548.1285977377@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Josh Berkus <josh@agliodbs.com> writes:
> The issue is this: when a partitioned table is evaluated by the planner
> for constraint exclusion, it evaluates ALL check constraints on each
> partition, regardless of whether or not they include a referenced column
> in the query (and whether or not they relate to partitioning).

[ shrug ... ]  We do not promise that the current partitioning scheme
scales to the number of partitions where this is likely to be an
interesting concern.

*After* we have a real partitioning scheme, it might be worth worrying
about this sort of problem, if it's still a problem then.

> Are we talking "moderate", "hard" or "nearly impossible"?

We're talking "wasted effort on a dead-end situation".  The time that
would go into this would be much better spent on real partitioning.

			regards, tom lane