From: Tom Lane <tgl@sss.pgh.pa.us>
To: David G. Johnston <david.g.johnston@gmail.com>
Cc: jian he <jian.universality@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
Subject: Re: (record = record) inconsistent with record_eq(arg1, arg2)
Date: Mon, 31 Jul 2023 16:07:04 -0400
Message-ID: <2947561.1690834024@sss.pgh.pa.us> (raw)
In-Reply-To: <CAKFQuwYEw-f6RSP0xzUNNMus=OcyGX-6GSOPorb3YtRPPEiyxg@mail.gmail.com>
References: <CACJufxF6T4-vOqg1eu_JGrXszTUaHUmmjzCQUcuF6W56dhS+Vw@mail.gmail.com>
<CAKFQuwYEw-f6RSP0xzUNNMus=OcyGX-6GSOPorb3YtRPPEiyxg@mail.gmail.com>
"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Monday, July 31, 2023, jian he <jian.universality@gmail.com> wrote:
>> select row(1,null::int) = (1,1::int); -- return null
>> select record_eq(row(1,null::int),(1,1::int)); --return false.
> This isn’t a bug though I can’t point to the exact code where the
> difference manifests.
Yeah, the difference in behavior is deliberate. See
https://www.postgresql.org/docs/current/functions-comparisons.html#ROW-WISE-COMPARISON
which documents the behavior of ROW(...) = ROW(...), and
https://www.postgresql.org/docs/current/functions-comparisons.html#COMPOSITE-TYPE-COMPARISON
which documents the behavior of record comparisons that are written
in other ways, and explains the reason for the difference. The
SQL standard governs the behavior of "ROW(...) = ROW(...)", but last
I looked they don't really have a notion of composite-valued scalars,
so the spec has nothing to say about what "row-valued-expression =
row-valued-expression" should do. Even if it did, we would not
change this, because it's too important to have a total ordering
for composite columns.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, david.g.johnston@gmail.com, jian.universality@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: (record = record) inconsistent with record_eq(arg1, arg2)
In-Reply-To: <2947561.1690834024@sss.pgh.pa.us>
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