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Re: Calculation of unused columns

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Volker Grabsch <vog(at)notjusthosting(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Calculation of unused columns
Date: 2009-10-18 01:53:11
Message-ID: 603c8f070910171853l5f2a81ai71f00417f8a2e959@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Sat, Oct 17, 2009 at 9:41 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I've been thinking about this since your earlier mail, and I think it
> would probably be possible to suppress unused columns in a non-flattened
> subquery.  I remain unconvinced that it's worth the trouble though.
> A real (not handwavy) example would help make the case here.

Are there any situations where this would enable join removal that
otherwise wouldn't be possible?  Maybe a query involving an
unflattenable VIEW?

...Robert

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