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From: Junwang Zhao <zhjwpku@gmail.com>
Date: Fri, 6 Feb 2026 14:19:11 +0800
Message-ID: <CAEG8a3KBQjfY9zu8F7NGX=g-7B-mW3-U7bD+OLQ0cFeFzigDkw@mail.gmail.com>
Subject: Re: Emitting JSON to file using COPY TO
To: jian he <jian.universality@gmail.com>
Cc: Florents Tselai <florents.tselai@gmail.com>, Joe Conway <mail@joeconway.com>, 
	"Andrey M. Borodin" <x4mmm@yandex-team.ru>, Dean Rasheed <dean.a.rasheed@gmail.com>, 
	Daniel Verite <daniel@manitou-mail.org>, Andrew Dunstan <andrew@dunslane.net>, 
	Davin Shearer <davin@apache.org>, PostgreSQL-development <pgsql-hackers@postgresql.org>
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On Fri, Feb 6, 2026 at 11:26=E2=80=AFAM jian he <jian.universality@gmail.co=
m> wrote:
>
> On Wed, Feb 4, 2026 at 12:41=E2=80=AFAM Florents Tselai
> <florents.tselai@gmail.com> wrote:
> >
> > I (and others I assume) would really like to see this in 19;
> > glancing at the thread above and in the test cases I see this is in goo=
d shape for comitter review.
> > No?
> >
> > If I were to add something  it would be an example in copy.sgml
> >   <para>
> >    When the <literal>FORCE_ARRAY</literal> option is enabled,
> >    the entire output is wrapped in a JSON array and individual rows are=
 separated by commas:
> >    <programlisting>
> > COPY (SELECT id, name FROM users) TO STDOUT (FORMAT JSON, FORCE_ARRAY);
> >    </programlisting>
> >    <programlisting>
> > [
> > {"id": 1, "name": "Alice"}
> > ,{"id": 2, "name": "Bob"}
> > ,{"id": 3, "name": "Charlie"}
> > ]
> >    </programlisting>
> >   </para>
> >
>
> v23-0003-Add-option-force_array-for-COPY-JSON-FORMAT.patch
> I've added:
>
> +<para>
> +   When the <literal>FORCE_ARRAY</literal> option is enabled,
> +   the entire output is wrapped in a single JSON array with rows
> separated by commas:
> +<programlisting>
> +COPY (SELECT * FROM (VALUES(1),(2)) val(id)) TO STDOUT  (FORMAT JSON,
> FORCE_ARRAY);
> +</programlisting>
> +The output is as follows:
> +<screen>
> +[
> + {"id":1}
> +,{"id":2}
> +]
> +</screen>
> +</para>
> +
> +
>
> > Also, apologies if that has been discussed already,
> > is there a good reason why didn't we just go with a simple "WRAP_ARRAY"=
 ?
> >
>
> I don=E2=80=99t have a particular preference.
> If the consensus is that WRAP_ARRAY is better than FORCE_ARRAY, we can
> change it accordingly.

+0.5 for WRAP_ARRAY

>
>
> --
> jian
> https://www.enterprisedb.com/


--=20
Regards
Junwang Zhao