Re: Planner matching constants across tables in a join

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Richard Huxton <dev(at)archonet(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Planner matching constants across tables in a join
Date: 2003-03-05 15:08:38
Message-ID: 19225.1046876918@sss.pgh.pa.us
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Greg Stark <gsstark(at)mit(dot)edu> writes:
> Richard Huxton <dev(at)archonet(dot)com> writes:
>> If I join two tables with a comparison to a constant on one, why can't the
>> planner see that the comparison applies to both tables:

> It sure does. Postgres does an impressive job of tracing equality clauses
> around for just this purpose.

CVS tip does. Existing releases don't...

regards, tom lane

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