From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
Cc: | PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "James Pang (chaolpan)" <chaolpan(at)cisco(dot)com> |
Subject: | Re: extended statistics n-distinct on multiple columns not used when join two tables |
Date: | 2023-06-13 11:28:34 |
Message-ID: | CAFj8pRCQ5bXt_kDtoQRk=D0voVo_Wwj70SfrS19+dZHbAr3hsw@mail.gmail.com |
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Lists: | pgsql-hackers pgsql-performance |
út 13. 6. 2023 v 13:26 odesílatel David Rowley <dgrowleyml(at)gmail(dot)com>
napsal:
> (moving to -hackers)
>
> On Tue, 13 Jun 2023 at 21:30, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
> > út 13. 6. 2023 v 11:21 odesílatel James Pang (chaolpan) <
> chaolpan(at)cisco(dot)com> napsal:
> >> When join two table on multiple columns equaljoin, rows estimation
> always use selectivity = multiplied by distinct multiple individual
> columns, possible to use extended n-distinct statistics on multiple
> columns?
> >>
> >> PG v14.8-1, attached please check test case with details.
> >
> > There is not any support for multi tables statistic
>
> I think it's probably worth adjusting the docs to mention this. It
> seems like it might be something that could surprise someone.
>
> Something like the attached, maybe?
>
+1
Pavel
> David
>
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