On Mon, Apr 20, 2026 at 11:25 PM jian he <jian.universality@gmail.com> wrote:
>
> On Thu, Apr 16, 2026 at 7:26 AM 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 = 999 WHERE id = 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%3DyGvDAyeFEuvkmeQx448-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,
--
Paul ~{:-)
pj@illuminatedcomputing.com
