Re: inefficient query plan with left joined view

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andreas Pflug <Andreas(dot)Pflug(at)web(dot)de>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: inefficient query plan with left joined view
Date: 2003-01-28 22:41:00
Message-ID: 4509.1043793660@sss.pgh.pa.us
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Andreas Pflug <Andreas(dot)Pflug(at)web(dot)de> writes:
> As the example shows even
> columns that are never used will be taken into account when checking
> has_nullable_targetlist.

It's not really practical to do otherwise, as the code that needs to
check this doesn't have access to a list of the columns actually used.
Even if we kluged things up enough to make it possible to find that out,
that would merely mean that *some* of your queries wouldn't have a
problem.

What about improving the intelligence of the nullability check --- or do
you have non-strict expressions in there?

regards, tom lane

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