Re: sequential scan on select distinct

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От Tom Lane
Тема Re: sequential scan on select distinct
Дата
Msg-id 29194.1097091506@sss.pgh.pa.us
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Ответ на Re: sequential scan on select distinct  (Greg Stark <gsstark@mit.edu>)
Ответы Re: sequential scan on select distinct  (Greg Stark <gsstark@mit.edu>)
Re: sequential scan on select distinct  (Pierre-Frédéric Caillaud<lists@boutiquenumerique.com>)
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Greg Stark <gsstark@mit.edu> writes:
> why isn't a "skip index scan" plan available? Well, nobody's written the code
> yet.

I don't really think it would be a useful plan anyway.  What *would* be
useful is to support HashAggregate as an implementation alternative for
DISTINCT --- currently I believe we only consider that for GROUP BY.
The DISTINCT planning code is fairly old and crufty and hasn't been
redesigned lately.

            regards, tom lane

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