Re: BUG #17700: An assert failed in prepjointree.c - Mailing list pgsql-bugs

From Richard Guo
Subject Re: BUG #17700: An assert failed in prepjointree.c
Date
Msg-id CAMbWs488fY3pzOoBwDNJijrhAtmkmbETaVQHmKaRS3HG6jbzLg@mail.gmail.com
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In response to Re: BUG #17700: An assert failed in prepjointree.c  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: BUG #17700: An assert failed in prepjointree.c  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-bugs

On Tue, Nov 29, 2022 at 10:24 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
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.
 
Hmm, I see your point.  You're right.  'c2 fulljoin c3' would be reduced
to 'c3 leftjoin c2'.

BTW, I wonder if we need the JOIN_RIGHT case here since JOIN_RIGHT
should have been flipped around to become JOIN_LEFT.

Thanks
Richard

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