Re: Calculation of unused columns - Mailing list pgsql-performance

From Tom Lane
Subject Re: Calculation of unused columns
Date
Msg-id 28393.1255832373@sss.pgh.pa.us
Whole thread Raw
In response to Re: Calculation of unused columns  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: Calculation of unused columns  (Daniel Migowski <dmigowski@ikoffice.de>)
List pgsql-performance
Robert Haas <robertmhaas@gmail.com> writes:
> On Sat, Oct 17, 2009 at 9:41 PM, Tom Lane <tgl@sss.pgh.pa.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?

Hmm, yeah maybe, now that we have some join removal logic.  Seems a bit
of a stretch to claim that's a common real-world case though.

            regards, tom lane

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