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Message-ID: <afb7be67-cc8a-42b9-952a-0bd7e8c9f925@gmail.com>
Date: Tue, 24 Jun 2025 10:00:00 +0300
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Subject: Re: BUG #18953: Planner fails to build plan for complex query with
 LATERAL references
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-bugs@lists.postgresql.org, Richard Guo <guofenglinux@gmail.com>
References: <18953-1c9883a9d4afeb30@postgresql.org>
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 <1268645.1749765012@sss.pgh.pa.us> <1499514.1749848324@sss.pgh.pa.us>
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 <527134.1750087495@sss.pgh.pa.us>
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 <835659.1750177751@sss.pgh.pa.us>
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 <3040798.1750617116@sss.pgh.pa.us> <3886446.1750703041@sss.pgh.pa.us>
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From: Alexander Lakhin <exclusion@gmail.com>
In-Reply-To: <3886446.1750703041@sss.pgh.pa.us>
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Hello Tom and Richard,

23.06.2025 21:24, Tom Lane wrote:
> Anyway, with one eye on the possibility that we'll need to back-patch
> this in some form, I went for the localized fix of ensuring that
> we use a copy of the PHV that's been through the normal processing.
> I do want to look into restructuring the handling of these PHVs
> to make this less messy, but that's not a job to undertake for v18
> (much less if we have to back-patch).

I've managed to discover one more anomaly introduced by a16ef313f, that is
not fixed by fix-bug-18953-some-more:
CREATE TABLE t(i int PRIMARY KEY);

MERGE INTO t
USING
   (SELECT 1 AS j FROM generate_series(1, 1))
   RIGHT JOIN (SELECT 1) ON true
   LEFT JOIN (SELECT 1 FROM (SELECT 1 FROM generate_series(1, 1))) ON false
ON i = j
WHEN NOT MATCHED THEN INSERT VALUES (1);
ERROR:  XX000: wrong phnullingrels (b) (expected (b 4)) for PlaceHolderVar 1
LOCATION:  search_indexed_tlist_for_phv, setrefs.c:2958

Thank you for spending your time on this!

Best regards,
Alexander
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    <div class="moz-cite-prefix">Hello Tom and Richard,<br>
      <br>
      23.06.2025 21:24, Tom Lane wrote:<span
      style="white-space: pre-wrap">
</span></div>
    <blockquote type="cite" cite="mid:3886446.1750703041@sss.pgh.pa.us">
      <pre wrap="" class="moz-quote-pre">Anyway, with one eye on the possibility that we'll need to back-patch
this in some form, I went for the localized fix of ensuring that
we use a copy of the PHV that's been through the normal processing.
I do want to look into restructuring the handling of these PHVs
to make this less messy, but that's not a job to undertake for v18
(much less if we have to back-patch).
</pre>
    </blockquote>
    <br>
    I've managed to discover one more anomaly introduced by a16ef313f,
    that is<br>
    not fixed by fix-bug-18953-some-more:<br>
    CREATE TABLE t(i int PRIMARY KEY);<br>
    <br>
    MERGE INTO t<br>
    USING<br>
      (SELECT 1 AS j FROM generate_series(1, 1))<br>
      RIGHT JOIN (SELECT 1) ON true<br>
      LEFT JOIN (SELECT 1 FROM (SELECT 1 FROM generate_series(1, 1))) ON
    false<br>
    ON i = j<br>
    WHEN NOT MATCHED THEN INSERT VALUES (1);<br>
    ERROR:  XX000: wrong phnullingrels (b) (expected (b 4)) for
    PlaceHolderVar 1<br>
    LOCATION:  search_indexed_tlist_for_phv, setrefs.c:2958<br>
    <br>
    Thank you for spending your time on this!<br>
    <br>
    Best regards,<br>
    Alexander<br>
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