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From: Richard Guo <guofenglinux@gmail.com>
Date: Tue, 21 Apr 2026 12:20:02 +0900
Message-ID: <CAMbWs4_vqNEcHpvKFeFxfRoisrvw6yJ3styhS-arQDHZirw5cQ@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>
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On Tue, Apr 21, 2026 at 11:30=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wrote=
:
> 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.

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