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Re: optimizing constant quals within outer joins

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Phil Frost <indigo(at)bitglue(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: optimizing constant quals within outer joins
Date: 2006-06-28 15:40:52
Message-ID: 15723.1151509252@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Phil Frost <indigo(at)bitglue(dot)com> writes:
> The planner in fact can move the function around without changing the
> output.

Not when it's within the nullable side of an outer join --- moving a
WHERE clause up out of that would make the difference between no row
out, and a null-extended row out, which are certainly not the same.

I'm not sure why it's not pulling up from the left side of the left join
though.  That might be a bug.  What PG version is this exactly?

Of course the real question is why is your app generating such poorly
phrased queries ;-)

			regards, tom lane

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