From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Robins Tharakan <tharakan@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17781: Assert in setrefs.c
Date: Wed, 08 Feb 2023 12:11:52 -0500
Message-ID: <3499087.1675876312@sss.pgh.pa.us> (raw)
In-Reply-To: <CAMbWs4_aiLNvBw8w2YSZFcU9Z-yKV5pKB+AKsrWJgp8y+r2hcg@mail.gmail.com>
References: <17781-c0405c8b3cd5e072@postgresql.org>
<3384987.1675812417@sss.pgh.pa.us>
<CAEP4nAzgCUWd1RWq81Twpud2yAkZejMRqfSoKbvMsdEqHq4KBg@mail.gmail.com>
<CAMbWs4_ngw9sKxpTE8hqk=-ooVX_CQP3DarA4HzkRMz_JKpTrA@mail.gmail.com>
<CAMbWs4_aiLNvBw8w2YSZFcU9Z-yKV5pKB+AKsrWJgp8y+r2hcg@mail.gmail.com>
Richard Guo <guofenglinux@gmail.com> writes:
> Hmm. I begin to wonder if it's better to use phinfo->ph_eval_at instead
> in build_joinrel_tlist when we check whether the PHV actually comes from
> the nullable side of an outer join.
I wondered about that too, but I think phrels is probably preferable,
because it is fundamentally a syntactic attribute and what we are
after here is matching the syntactic structure. I could be convinced
that that's wrong, but I'd want to see an actual counterexample.
> Even so it seems we still need to update phv->phrels in
> remove_rel_from_query when we remove a left join. Otherwise it'd be
> weird to observe that phrels contains some already-removed relids.
Agreed, that's a good catch. As the comment for remove_rel_from_query
says,
* We are not terribly thorough here.
It's not surprising that the requirements for it advance over time.
(At one point I wrote some code that taught it to clean out the
removed relids from EquivalenceClasses, which doesn't need
to happen right now because we don't ever put outer-join quals
into EquivalenceClasses. I don't think I included that in any
of the published versions of the patch series, but it's going to
need to reappear eventually.)
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, guofenglinux@gmail.com, tharakan@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17781: Assert in setrefs.c
In-Reply-To: <3499087.1675876312@sss.pgh.pa.us>
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