From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Richard Guo <guofenglinux(at)gmail(dot)com> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Assert failure of the cross-check for nullingrels |
Date: | 2023-05-19 19:29:16 |
Message-ID: | 354925.1684524556@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Richard Guo <guofenglinux(at)gmail(dot)com> writes:
> I keep thinking about my proposal in v2 patch. It seems more natural to
> me to fix this issue, because an outer join's quals are always treated
> as a whole when we check if identity 3 applies in make_outerjoininfo, as
> well as when we adjust the outer join's quals for commutation in
> deconstruct_distribute_oj_quals.
No, I doubt that that patch works properly. If the join condition
contains independent quals on different relations, say
select ... from t1 left join t2 on (t1.a = 1 and t2.b = 2)
then it may be that those quals need to be pushed to different levels.
I don't believe that considering the union of the rels mentioned in
any qual is a reasonable thing to do here.
regards, tom lane
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