Re: Order by (for 15 rows) adds 30 seconds to query time

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От Tom Lane
Тема Re: Order by (for 15 rows) adds 30 seconds to query time
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Msg-id 21616.1259785526@sss.pgh.pa.us
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Ответ на Re: Order by (for 15 rows) adds 30 seconds to query time  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
Ответы Re: Order by (for 15 rows) adds 30 seconds to query time  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
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"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Craig Ringer <craig@postnewspapers.com.au> wrote:
>> Doesn't the planner have some ... issues ... with estimation of
>> row counts on joins over unions? Or is my memory just more faulty
>> than usual?

> So far I can't tell if it's views with unions or (as I suspect)
> inheritance.

As of recent versions there shouldn't be a lot of difference between
inheritance and UNION ALL subqueries --- they're both "appendrels"
to the planner.  And yeah, I think the statistical support is pretty
crummy.

            regards, tom lane

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