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From: Paul A Jungwirth <pj@illuminatedcomputing.com>
Date: Wed, 22 Apr 2026 12:50:27 -0700
Message-ID: 
 <CA+renyVUL52kYNTuO1e=wp8D8Ey9=xazfpSTrGJ0R48Ps=A-Jg@mail.gmail.com>
Subject: Re: SQL:2011 Application Time Update & Delete
To: jian he <jian.universality@gmail.com>
Cc: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>,
 Peter Eisentraut <peter@eisentraut.org>,
	Chao Li <li.evan.chao@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Mon, Apr 20, 2026 at 11:25=E2=80=AFPM jian he <jian.universality@gmail.c=
om> wrote:
>
> On Thu, Apr 16, 2026 at 7:26=E2=80=AFAM Paul A Jungwirth
> <pj@illuminatedcomputing.com> wrote:
> >
> > I think using INSTEAD OF triggers to replace an UPDATE/DELETE FOR
> > PORTION OF is a valid use-case, but it doesn't make sense to insert
> > temporal leftovers. As you say, we can't access the underlying
> > storage. But also we don't know what changes the trigger actually
> > made. The trigger should be responsible for leftovers, and we
> > shouldn't try to add more. So I think the fix is just to skip
> > inserting leftovers. I've attached a patch to do that.
> >
> hi.
>
> CREATE TABLE fpo_instead_base (id int, valid_at daterange, val int);
> INSERT INTO fpo_instead_base VALUES (1, '[2024-01-01,2024-12-31)', 100);
> CREATE VIEW fpo_instead_view AS SELECT * FROM fpo_instead_base;
> CREATE FUNCTION fpo_instead_trig_fn() RETURNS trigger LANGUAGE plpgsql AS=
 $$
> BEGIN
>     RETURN NEW;
> END;
> $$;
> CREATE TRIGGER fpo_instead_trig INSTEAD OF UPDATE ON fpo_instead_view
>   FOR EACH ROW EXECUTE FUNCTION fpo_instead_trig_fn();
>
> UPDATE fpo_instead_view FOR PORTION OF valid_at FROM '2024-04-01' TO
> '2024-08-01'
>     SET val =3D 999 WHERE id =3D 1
>     RETURNING *;
>
>  id |        valid_at         | val
> ----+-------------------------+-----
>   1 | [2024-01-01,2024-12-31) | 999
> (1 row)
>
> Should I expect the column `valid_at` value as [2024-04-01,2024-08-01) ?

Yes, because we ran an INSTEAD OF trigger and skipped the UPDATE
(including setting the start/end dates).

> We should also document this on doc/src/sgml/ref/update.sgml
> Attached is a minor regession test enhancement for
> "v2-0001-Fix-INSTEAD-OF-triggers-with-DELETE-UPDATE-FOR-PO.patch".

Thanks! I squashed those patches and did some minor cleanup. I posted
v4 to this dedicated thread:
https://www.postgresql.org/message-id/CA%2BrenyVenLk%2Bu%3DyGvDAyeFEuvkmeQx=
448-KnnGczqQHB10_fbg%40mail.gmail.com

I also made a commitfest entry pointing there. Let's continue on that
thread so that future messages & patches get tracked correctly (and
not as part of the original feature's CF entry).

Hmm I forgot to add the documentation first. So I'll do that and post
a v5 shortly.

Yours,

--=20
Paul              ~{:-)
pj@illuminatedcomputing.com