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In-Reply-To: <C2133B47-79CD-40FF-B088-02D20D654806@gmail.com>
From: Amit Langote <amitlangote09@gmail.com>
Date: Fri, 3 Apr 2026 18:39:48 +0900
Message-ID: 
 <CA+HiwqFx=aciJYkkaviyTutUm303QXz6GtXSqzG7nfd4MAzddQ@mail.gmail.com>
Subject: Re: Eliminating SPI / SQL from some RI triggers - take 3
To: Chao Li <li.evan.chao@gmail.com>
Cc: Junwang Zhao <zhjwpku@gmail.com>, Haibo Yan <tristan.yim@gmail.com>,
	Pavel Stehule <pavel.stehule@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>,
 Tomas Vondra <tomas@vondra.me>
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On Fri, Apr 3, 2026 at 5:58=E2=80=AFPM Chao Li <li.evan.chao@gmail.com> wro=
te:
> > On Apr 3, 2026, at 13:52, Amit Langote <amitlangote09@gmail.com> wrote:
> > On Thu, Apr 2, 2026 at 5:00=E2=80=AFPM Chao Li <li.evan.chao@gmail.com>=
 wrote:
> >> I plan to spend time testing and tracing this patch tomorrow. But I do=
n=E2=80=99t want to block your progress, if I find anything, I will report =
to you.
> >
> > Sure, I didn't want to leave committing this to the weekend or the next=
 week.
>
> I spent several hours debugging this patch today, and I found a problem w=
here the batch mode doesn't seem to handle deferred RI triggers, although t=
he commit message suggests that it should.
>
> I traced this scenario:
> ```
> CREATE TABLE pk (a int primary key);
> CREATE TABLE fk (a int references pk(a) DEFERRABLE INITIALLY DEFERRED);
> BEGIN;
> INSERT INTO fk VALUES (1);
> INSERT INTO pk VALUES (1);
> COMMIT;
> ```
>
> When COMMIT is executed, it reaches RI_FKey_check(), where AfterTriggerIs=
Active() checks whether afterTriggers.query_depth >=3D 0. But in the deferr=
ed case, afterTriggers.query_depth is -1.
>
> From the code:
> ```
>         if (ri_fastpath_is_applicable(riinfo))
>         {
>                 if (AfterTriggerIsActive())
>                 {
>                         /* Batched path: buffer and probe in groups */
>                         ri_FastPathBatchAdd(riinfo, fk_rel, newslot);
>                 }
>                 else
>                 {
>                         /* ALTER TABLE validation: per-row, no cache */
>                         ri_FastPathCheck(riinfo, fk_rel, newslot);
>                 }
>                 return PointerGetDatum(NULL);
>         }
> ```
>
> So this ends up falling back to the per-row path for deferred RI checks a=
t COMMIT, even though the intent here seems to be only to bypass the ALTER =
TABLE validation case, where batch callbacks would never fire, and MyTrigge=
rDepth is 0. So, maybe we can just check MyTriggerDepth>0 in AfterTriggerIs=
Active().
>
> I tried the attached fix. With it, deferred triggers go through the batch=
 mode, and all existing tests still pass.

I think you might be right.  Thanks for the patch.  It looks correct
to me at a glance, but I will need to check it a bit more closely
before committing.

--=20
Thanks, Amit Langote