Re: A problem about partitionwise join

From: Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>
To: Richard Guo <guofenglinux(at)gmail(dot)com>
Cc: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Richard Guo <riguo(at)pivotal(dot)io>, ashutosh(dot)bapat(at)enterprisedb(dot)com
Subject: Re: A problem about partitionwise join
Date: 2021-10-05 17:19:22
Message-ID: 20211005171922.GB28628@ahch-to
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On Wed, Jul 21, 2021 at 04:44:53PM +0800, Richard Guo wrote:
> On Fri, Nov 27, 2020 at 8:05 PM Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
> wrote:
> >
> > In the example you gave earlier, the equi join on partition key was
> > there but it was replaced by individual constant assignment clauses.
> > So if we keep the original restrictclause in there with a new flag
> > indicating that it's redundant, have_partkey_equi_join will still be
> > able to use it without much change. Depending upon where all we need
> > to use avoid restrictclauses with the redundant flag, this might be an
> > easier approach. However, with Tom's idea partition-wise join may be
> > used even when there is no equi-join between partition keys but there
> > are clauses like pk = const for all tables involved and const is the
> > same for all such tables.
> >
> Correct. So with Tom's idea partition-wise join can cope with clauses
> such as 'foo.k1 = bar.k1 and foo.k2 = 16 and bar.k2 = 16'.
> >
> > In the spirit of small improvement made to the performance of
> > have_partkey_equi_join(), pk_has_clause should be renamed as
> > pk_known_equal and pks_known_equal as num_equal_pks.
> >
> Thanks for the suggestion. Will do that in the new version of patch.

Hi Richard,

We are marking this CF entry as "Returned with Feedback", which means
you are encouraged to send a new patch (and create a new entry for a
future CF for it) with the suggested changes.

Jaime Casanova
Director de Servicios Profesionales
SystemGuards - Consultores de PostgreSQL

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