Re: [PATCH] Fix null pointer dereference in PG19

On Thu, Jun 25, 2026 at 3:32 AM Aleksander Alekseev
<aleksander@tigerdata.com> wrote:
>
> This patch rotted and needed a rebase (attached as .txt).

Thank you for taking care of the rebase!

> Also it's
> incorrect, it only masks the crash:
>
> ```
> CREATE TABLE t (id int, valid_at daterange, val int);
> INSERT INTO t VALUES (1, '[2024-01-01,2025-01-01)', 100);
> CREATE VIEW v AS SELECT * FROM t;
>
> CREATE FUNCTION trig_fn() RETURNS trigger LANGUAGE plpgsql AS $$
> BEGIN
>     RAISE NOTICE 'UPDATE OLD: %, NEW: %', OLD, NEW;
>     RETURN NEW;
> END;
> $$;
>
> CREATE TRIGGER trig INSTEAD OF UPDATE ON v FOR EACH ROW EXECUTE
> FUNCTION trig_fn();
> UPDATE v FOR PORTION OF valid_at FROM '2024-04-01' TO '2024-08-01' SET
> val = 999 WHERE id = 1;
>
> server closed the connection unexpectedly
> ```

You're right, this was due to a copy/paste bug (looking for a delete
trigger in the update code). By splitting the test into two triggers,
we catch the problem and correctly skip the leftovers. I've attached a
patch with that correction.

> IMO it's a little bit late in the PG19 cycle for making this work.
> This is an implementation of a new feature which is not present at the
> moment which to my knowledge we don't do after the feature freeze. Our
> goal is to fix the crash and leave the rest for the PG20 cycle.
> Clearly the feature needs more discussion and thorough testing.

I don't really think this is a new feature. It is a fix to make FOR
PORTION OF not execute when it shouldn't. The change here is quite
simple.

But I don't mind holding it back if that's what people want to do.
Looking more closely at INSTEAD OF triggers, I found another bug: the
FOR PORTION OF qual (and TLE) were not added, so the trigger would
fire on more rows than it should, and NEW.valid_at was not
pre-computed. The second patch here fixes that. I'll defer to others
whether we should fix the INSTEAD OF interaction now or wait 'til v20.

Yours,

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