From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: Daniel Gustafsson <daniel@yesql.se>, xinwen@stu.scu.edu.cn,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17700: An assert failed in prepjointree.c
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Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
	message dated "Tue, 29 Nov 2022 10:19:00 +0800"
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Date: Mon, 28 Nov 2022 21:24:13 -0500
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Richard Guo <guofenglinux@gmail.com> writes:
> BTW, for the test case

> +explain (verbose, costs off)
> +with ctetable as not materialized ( select 1 as f1 )
> +select * from ctetable c1
> +where f1 in ( select c3.f1 from ctetable c2 full join ctetable c3 on true
> );

> Actually we just need to keep 'c3' in a join's nullable side to have the
> PHV created.  So we don't have to use full join in the subquery.  A left
> join would do.

Actually, the planner reduces the full join to left join anyway;
if it did not, it wouldn't be able to reach the code in question.
I think this formulation is fine because it tests that step along
with the bug proper.

			regards, tom lane