| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Regression in join selectivity estimations when using foreign keys |
| Date: | 2017-06-20 22:13:18 |
| Message-ID: | CAKJS1f9dzWgNNsQrJpu2uN_Cp=zXRBOAQ0cEMb5BD2do6izd+A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 20 June 2017 at 07:49, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm not totally satisfied that there isn't any case where the smallest
> selectivity hack is appropriate. In the example you're showing here,
> the FK columns are independent so that we get more or less the right
> answer with or without the FK. But in some quick testing I could not
> produce a counterexample proving that that heuristic is helpful;
> so for now let's can it.
>
> Thanks, and sorry again for the delay.
Many thanks for taking the time on this.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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