From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter@eisentraut.org>
cc: "David E. Wheeler" <david@justatheory.com>,
        jian he <jian.universality@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Document DateStyle effect on jsonpath string()
In-reply-to: <5e8879d0-a3c8-4be2-950f-d83aa2af953a@eisentraut.org>
References: <56955B33-6959-4FDA-A459-F00363ECDFEE@justatheory.com> <CACJufxHREyTFzKOWz3f-yD14HxAdfeP1vGQQ2SQrusZ+ziRJyA@mail.gmail.com> <4D874C72-8939-4083-8336-AB114D9E29AD@justatheory.com> <CACJufxHE6q47-GEf3Kk0pD+Snr3yZMM4Byig2=bQKV8js7sP-A@mail.gmail.com> <B8E7081B-A8BE-4BAF-9C6B-AACD4F6EAB00@justatheory.com> <F492B399-37CB-471C-AEAD-25E1C19B607D@justatheory.com> <A556B643-F7E6-442D-9235-2D46A8A887C1@justatheory.com> <3541398.1725994308@sss.pgh.pa.us> <D6137AEA-0BE7-4328-9718-71B7E6BB4F6C@justatheory.com> <b847bc16-57b4-4701-870b-c4ed33d71e51@eisentraut.org> <3654686.1725999372@sss.pgh.pa.us> <5e8879d0-a3c8-4be2-950f-d83aa2af953a@eisentraut.org>
Comments: In-reply-to Peter Eisentraut <peter@eisentraut.org>
	message dated "Wed, 11 Sep 2024 12:20:41 +0200"
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Date: Wed, 11 Sep 2024 10:11:05 -0400
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Peter Eisentraut <peter@eisentraut.org> writes:
> What I'm concerned about is that this makes the behavior of JSON_QUERY =

> non-immutable.  Maybe there are other reasons for it to be =

> non-immutable, in which case this isn't important.  But it might be =

> worth avoiding that?

Fair point, but haven't we already bit that bullet with respect
to timezones?

[ looks... ]  Hmm, it looks like jsonb_path_exists_tz is marked
stable while jsonb_path_exists is claimed to be immutable.
So yeah, there's a problem here.  I'm not 100% convinced that
jsonb_path_exists was truly immutable before, but for sure it
is not now, and that's bad.

regression=3D# select jsonb_path_query('"2023-08-15 12:34:56"', '$.timesta=
mp().string()');
   jsonb_path_query    =

-----------------------
 "2023-08-15 12:34:56"
(1 row)

regression=3D# set datestyle =3D postgres;
SET
regression=3D# select jsonb_path_query('"2023-08-15 12:34:56"', '$.timesta=
mp().string()');
      jsonb_path_query      =

----------------------------
 "Tue Aug 15 12:34:56 2023"
(1 row)

			regards, tom lane