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From: Richard Guo <guofenglinux@gmail.com>
Date: Thu, 23 Apr 2026 09:55:10 +0900
Message-ID: <CAMbWs49ps9eGWvkwc64ytUxdK0s-=xdFjtf64WyGp65EgTZ_LQ@mail.gmail.com>
Subject: Re: BUG #19418: SQL/JSON JSON_VALUE() does not conform to ISO/IEC
 9075-2:2023(E) 6.34 <JSON value constructor>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Amit Langote <amitlangote09@gmail.com>, Vik Fearing <vik@postgresfriends.org>, 
	lukas.eder@gmail.com, pgsql-bugs@lists.postgresql.org, 
	rmt@lists.postgresql.org, =?UTF-8?Q?=C3=81lvaro_Herrera?= <alvherre@kurilemu.de>, 
	Nathan Bossart <nathandbossart@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, 
	Melanie Plageman <melanieplageman@gmail.com>
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On Tue, Apr 21, 2026 at 12:20=E2=80=AFPM Richard Guo <guofenglinux@gmail.co=
m> wrote:
>
> On Tue, Apr 21, 2026 at 11:30=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wro=
te:
> > Richard Guo <guofenglinux@gmail.com> writes:
> > > Another question I'd like to raise: is it OK to commit this patch to
> > > master given that feature freeze has passed?  I think the answer is
> > > yes, because this is arguably a bug fix rather than a new feature.
> > > However, it does change user-visible behavior, and existing app code
> > > that relies on the NULL behavior would break.  So if we commit it, we
> > > need to add in the release notes about this incompatibility.
>
> > Well, if we definitely intend to commit a compatibility-breaking
> > change, I think it's better to commit it sooner not later.  If we
> > wait till v20, all we accomplish is to give users another year to
> > write code that depends on the old behavior.
> >
> > However, usually at this stage of the cycle the answer to such
> > questions is "let the RMT decide".  Take the question to them
> > (cc'd).
>
> Thanks Tom for the suggestion.

Not sure the RMT mailing list works or not, maybe I'd better CC RMT
members.

- Richard

> Hi RMT,
>
> I'd like to commit a fix for JSON_ARRAY(subquery) behavior that
> involves a user-visible incompatibility, and would appreciate your
> go/no-go since we're past feature freeze.
>
> Summary:
>
> - JSON_ARRAY(SELECT ...) currently returns NULL over an empty result
> set, but the SQL/JSON standard requires it to return '[]'.  Fixing
> this changes user-visible output.
>
> - The same patch also fixes a deparsing issue: views defined with
> JSON_ARRAY(SELECT ...) are dumped back as the internal JSON_ARRAYAGG
> rewrite instead of the original syntax.
>
> - Richard