Re: Issue for partitioning with extra check constriants

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Issue for partitioning with extra check constriants
Date: 2010-10-01 23:56:17
Message-ID: 1548.1285977377@sss.pgh.pa.us
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Josh Berkus <josh(at)agliodbs(dot)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

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