Re: Slow PostgreSQL 10.6 query

Behrang Saeedzadeh <[email protected]> Mon, 7 Oct 2019 19:27:42 +1100

Newsgroups	gmane.comp.db.postgresql.performance
Message-ID	<CAERAJ+_KjAJJRvXp9B-x0rY1NNzw7EgZ-MoTku3-Op8ADuDhpQ@mail.gmail.com>

Thanks for the tip!

Regards,
Behrang (sent from my mobile)

On Mon, Oct 7, 2019, 07:37 Tomas Vondra <[email protected]>
wrote:

> On Tue, Oct 01, 2019 at 11:42:33PM +1000, Behrang Saeedzadeh wrote:
> >Thanks. That eliminated the bottleneck!
> >
> >Any ideas why adding ORDER BY to the subquery also changes the plan in a
> >way that eliminates the bottleneck?
> >
>
> IIRC the ORDER BY clause makes it impossible to "collapse" the subquery
> into the main (upper) one, and it probably happens to constrict the
> choices so that the planner ends up picking a good plan. I guess adding
> "OFFSET 0" to the subquery would have the same effect.
>
>
> regards
>
> --
> Tomas Vondra                  http://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>