From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tomasz Myrta <jasiek@klaster.net>
Cc: Jan Wieck <JanWieck@Yahoo.com>
Cc: Ries van Twisk <ries@jongert.nl>
Cc: pgsql-sql@postgresql.org
Subject: Re: To use a VIEW or not to use a View.....
Date: Wed, 22 Jan 2003 16:45:10 -0800 (PST)
Message-ID: <20030122164324.K4204-100000@megazone23.bigpanda.com> (raw)
In-Reply-To: <24368.1043271333@sss.pgh.pa.us>
On Wed, 22 Jan 2003, Tom Lane wrote:
> Stephan Szabo <sszabo@megazone23.bigpanda.com> writes:
> > The filter is applied only to a. So, if you really wanted the
> > c.a=3 condition to be applied for whatever reason you're out of
> > luck.
>
> FWIW, CVS tip is brighter: the condition does propagate to both relations.
>
> Hash Join (cost=22.51..45.04 rows=1 width=8)
> Hash Cond: ("outer".a = "inner".a)
> -> Seq Scan on a (cost=0.00..22.50 rows=5 width=4)
> Filter: (a = 3)
> -> Hash (cost=22.50..22.50 rows=5 width=4)
> -> Seq Scan on c (cost=0.00..22.50 rows=5 width=4)
> Filter: (3 = a)
>
> The reason this is useful is that (a) fewer rows need to be joined,
> and (b) we may be able to make effective use of indexes on both tables.
Yeah. I was going to ask how hard you thought it would be to do for
this particular sort of case. I thought about the simple case of using
and realized it'd probably be reasonable in amount of work, but it seems
I don't have to think about it. :)
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To: pgsql-sql@postgresql.org
Cc: sszabo@megazone23.bigpanda.com, tgl@sss.pgh.pa.us, jasiek@klaster.net, JanWieck@Yahoo.com, ries@jongert.nl
Subject: Re: To use a VIEW or not to use a View.....
In-Reply-To: <20030122164324.K4204-100000@megazone23.bigpanda.com>
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