RE: Why does not subquery pruning conditions inherit to parent query?

On Friday, May 31, 2019 9:33 PM, David Rowley wrote:
> On Fri, 31 May 2019 at 03:18, Kato, Sho <kato-sho(at)jp(dot)fujitsu(dot)com> wrote:
> > Is it possible to improve a subquery quals to pull up into outer query?
>
> Sure, it's possible, but it would require writing code. When it can and
> cannot/should not be done would need to be determined.

Is there any harmful effect by pulling up a subquery quals into outer query?

Even if this feature is not be needed, it will be a problem if user execute this query to a table partitioned into a lot.
So, I think it would be better to put together a query that partition pruning does not work on the wiki.
Thoughts?

Regards,
kato sho
> -----Original Message-----
> From: David Rowley [mailto:david(dot)rowley(at)2ndquadrant(dot)com]
> Sent: Friday, May 31, 2019 9:33 PM
> To: Kato, Sho/加藤 翔 <kato-sho(at)jp(dot)fujitsu(dot)com>
> Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>; pgsql-hackers(at)postgresql(dot)org
> Subject: Re: Why does not subquery pruning conditions inherit to parent
> query?
>
> On Fri, 31 May 2019 at 03:18, Kato, Sho <kato-sho(at)jp(dot)fujitsu(dot)com> wrote:
> > Is it possible to improve a subquery quals to pull up into outer query?
>
> Sure, it's possible, but it would require writing code. When it can and
> cannot/should not be done would need to be determined.
>
> --
> David Rowley http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training & Services
>
>