Re: PG19: two RI fast-path issues found while testing the batching revert

On Thu, Oct 22, 2026 at 8:16 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> On Thu, Oct 22, 2026 at 8:09 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> > On Thu, Oct 22, 2026 at 6:18 PM Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> > > On Thu, Oct 15, 2026 at 5:07 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> > > > > No, they have not. I’ll commit these today.
> > > >
> > > > Done, sorry for the delay.
> > >
> > > Commit 6aecabcd5ed seems to have caused a test failure on buildfarm
> > > member trilobite [1]. The log indicates that a client backend crashed
> > > with a segmentation fault:
> > >
> > > 2026-10-22 10:03:23.907 CEST [13117:8] LOG: client backend (PID
> > > 16078) was terminated by signal 11: Segmentation fault
> > > 2026-10-22 10:03:23.907 CEST [13117:9] DETAIL: Failed process was
> > > running: INSERT INTO fp_reentry_fk SELECT row(1)::fp_vch FROM
> > > generate_series(1, 2);
> > >
> > > Codex came up with the following minimal reproduction:
> > >
> > > --------------------------------------------------
> > > SET debug_discard_caches = 1;
> > >
> > > CREATE TABLE p (id int PRIMARY KEY);
> > > INSERT INTO p VALUES (1), (2);
> > > CREATE TYPE t AS (v int);
> > >
> > > CREATE FUNCTION c(t) RETURNS int LANGUAGE plpgsql AS $$
> > > BEGIN
> > > IF $1.v = 1 THEN
> > > INSERT INTO f VALUES (ROW(2)::t);
> > > END IF;
> > > RETURN $1.v;
> > > END$$;
> > >
> > > CREATE CAST (t AS int) WITH FUNCTION c(t) AS IMPLICIT;
> > > CREATE TABLE f (a t REFERENCES p);
> > > INSERT INTO f VALUES (ROW(1)::t);
> > > --------------------------------------------------
> > >
> > > This issue should be added into Open Items for v19?
> >
> > It's actually an old bug affecting all stable releases as I explained in:
> > https://postgr.es/m/CA+HiwqGZ9Rx5Lkh8+or4HK+jjHKQTZCgwgL50J=0mqL_9Cmu7g@mail.gmail.com
> >
> > Tom reported that same trilobite failure there.
> >
> > The patch for the same issue though with a different crashing example
> > is also being discussed here:
> > https://postgr.es/m/CA+HiwqGjcSqmsruvq94V0ARNx0Gec6Va9J-G2DQXafVKfEravQ@mail.gmail.com
> >
> > I am about to post a new patch at the second thread.
>
> To clarify, the test case that crashed trilobite started going through
> the SPI path instead of the fast path with 6aecabcd5ed. The SPI path
> has a bug that causes the crash, but the fast path doesn’t have the
> same bug. So the issue was not found until that commit made the test
> start going through the SPI path.

Sorry, I should also have mentioned that the test case was added as
part of the fast-path work so it had no chance of running through the
SPI path before 6aecabcd5.

--
Thanks, Amit Langote