From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Antonin Houska <ah(at)cybertec(dot)at>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Ordered Partitioned Table Scans |
Date: | 2019-03-24 10:05:58 |
Message-ID: | CAKJS1f-EPo-6h1UMFWOBrsdyxUWGZ1OTfoeu_wkiDPxXuB6usQ@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Sat, 23 Mar 2019 at 19:42, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
> > On Sat, 23 Mar 2019 at 05:40, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> BTW, another thing we could possibly do to answer this objection is to
> >> give the ordered-Append node an artificially pessimistic startup cost,
> >> such as the sum or the max of its children's startup costs. That's
> >> pretty ugly and unprincipled, but maybe it's better than not having the
> >> ability to generate the plan shape at all?
>
> > I admit to having thought of that while trying to get to sleep last
> > night, but I was too scared to even suggest it. It's pretty much how
> > MergeAppend would cost it anyway. I agree it's not pretty to lie
> > about the startup cost, but it does kinda seem silly to fall back on a
> > more expensive MergeAppend when we know fine well Append is cheaper.
>
> Yeah. I'm starting to think that this might actually be the way to go,
Here's a version with it done that way.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
Attachment | Content-Type | Size |
---|---|---|
mergeappend_to_append_conversion_v13.patch | application/octet-stream | 62.6 KB |
From | Date | Subject | |
---|---|---|---|
Next Message | Julien Rouhaud | 2019-03-24 10:24:50 | Re: Planning counters in pg_stat_statements (using pgss_store) |
Previous Message | David Rowley | 2019-03-24 10:00:39 | Re: Ordered Partitioned Table Scans |