From: Tom Lane <tgl@sss.pgh.pa.us>
To: exclusion@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18652: Planner can not find pathkey item to sort for query with expression and expression index
Date: Wed, 09 Oct 2024 17:43:03 -0400
Message-ID: <2527690.1728510183@sss.pgh.pa.us> (raw)
In-Reply-To: <18652-deaa782ebcca85d1@postgresql.org>
References: <18652-deaa782ebcca85d1@postgresql.org>
PG Bug reporting form <noreply@postgresql.org> writes:
> The following query:
> CREATE TABLE t(i int, j int);
> CREATE INDEX idx on t((i + 0));
> SELECT * FROM t,
> (SELECT i + 0 AS i FROM
> (SELECT i FROM t UNION ALL SELECT i + 1 FROM t) AS t1
> ) AS t2
> WHERE t2.i = t.j;
> fails with:
> ERROR: XX000: could not find pathkey item to sort
> LOCATION: prepare_sort_from_pathkeys, createplan.c:6350
> The error occurs only when the expression in SELECT i + 0 AS i FROM
> matches the expression in an index.
> Reproduced on REL_10_STABLE .. master.
Hm, this seems quite an old bug: I can reproduce it on 9.1 but
not 9.0. Unfortunately, that's too far back to build easily
on modern platforms, so I'm not seeing a way to "git bisect"
for more insight.
It looks like we are generating a Path tree in which one of the
inputs to a MergeAppend is a plain unsorted seqscan, which'd
be all right except it doesn't expose the required sort value
in its targetlist. More later.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18652: Planner can not find pathkey item to sort for query with expression and expression index
In-Reply-To: <2527690.1728510183@sss.pgh.pa.us>
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