Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtps
 (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1oQxmG-0004wf-5a
	for pgsql-hackers@arkaria.postgresql.org; Wed, 24 Aug 2022 21:19:08 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1oQxmE-0005pY-1w
	for pgsql-hackers@arkaria.postgresql.org; Wed, 24 Aug 2022 21:19:06 +0000
Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
	by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1oQxmD-0005pP-PC
	for pgsql-hackers@lists.postgresql.org; Wed, 24 Aug 2022 21:19:05 +0000
Received: from sss.pgh.pa.us ([66.207.139.130])
	by magus.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1oQxm7-0007vH-9j
	for pgsql-hackers@lists.postgresql.org; Wed, 24 Aug 2022 21:19:05 +0000
Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1])
	by sss.pgh.pa.us (8.15.2/8.15.2) with ESMTP id 27OLIrkF1165801;
	Wed, 24 Aug 2022 17:18:53 -0400
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>,
        "Finnerty,
    Jim" <jfinnert@amazon.com>
Subject: Re: Making Vars outer-join aware
In-reply-to: 
 <CAMbWs4_mSsoYQ2eOoQ7U6PQ9bugcjktg3KUtmt1+xaq+PUDMTw@mail.gmail.com>
References: <830269.1656693747@sss.pgh.pa.us>
 <CAMbWs49KZO2VvMqo+1MQfaX4cun7vhF=5RgVdpA0gjJcj77HFQ@mail.gmail.com>
 <1903934.1657031040@sss.pgh.pa.us> <553080.1657481916@sss.pgh.pa.us>
 <CAMbWs4-0cdVpgY0c2uULBCX2vPjQt3Fx3=XFZh-Mn=UWmxhG-A@mail.gmail.com>
 <1515100.1657633061@sss.pgh.pa.us>
 <CAMbWs4_va6UWcaiPSZpeRPFzpA=UKU+4zKkxqdfrcKoKA5nKWA@mail.gmail.com>
 <2217146.1657721363@sss.pgh.pa.us> <2055912.1659383493@sss.pgh.pa.us>
 <CAMbWs480igxj6hTbvD0WEnzT4XJ8hJXg71EVJO_BcQqN90MQuA@mail.gmail.com>
 <1188905.1660666103@sss.pgh.pa.us> <1405792.1660677844@sss.pgh.pa.us>
 <1538543.1660683428@sss.pgh.pa.us>
 <CAMbWs498oYx4pjzOsjxu0wG0D73e2+OFAqkbPotcSJDKzm-s4Q@mail.gmail.com>
 <2741731.1660848346@sss.pgh.pa.us> <3839865.1661035931@sss.pgh.pa.us>
 <CAMbWs4_mSsoYQ2eOoQ7U6PQ9bugcjktg3KUtmt1+xaq+PUDMTw@mail.gmail.com>
Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
	message dated "Wed, 24 Aug 2022 18:26:46 +0800"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1165799.1661375933.1@sss.pgh.pa.us>
Date: Wed, 24 Aug 2022 17:18:53 -0400
Message-ID: <1165800.1661375933@sss.pgh.pa.us>
List-Id: <pgsql-hackers.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-hackers@lists.postgresql.org>
List-Owner: <mailto:pgsql-hackers-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-hackers>
Archived-At: 
 <https://www.postgresql.org/message-id/1165800.1661375933%40sss.pgh.pa.us>
Precedence: bulk

Richard Guo <guofenglinux@gmail.com> writes:
> On Sun, Aug 21, 2022 at 6:52 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> What I'm thinking we should do about this, once we detect that
>> this identity is applicable, is to generate *both* forms of Pbc,
>> either adding or removing the varnullingrels bits depending on
>> which form we got from the parser.

> Do you mean we generate two RestrictInfos for Pbc in the case of
> identity 3, one with varnullingrels and one without varnullingrels, and
> choose the appropriate one when forming join paths?

Right.

> Do we need to also
> generate two SpecialJoinInfos for the B/C join in the first order, with
> and without the A/B join in its min_lefthand?

No, the SpecialJoinInfos would stay as they are now.  It's already the
case that the first join's min_righthand would contain only B, and
the second one's min_righthand would contain only C.

			regards, tom lane