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From: Amit Kapila <[email protected]>
To: Zhijie Hou (Fujitsu) <[email protected]>
Cc: Chao Li <[email protected]>
Cc: Nisha Moond <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Bug: wrong relname in RemoveSubscriptionRel() error detail
Date: Mon, 30 Mar 2026 17:49:41 +0530
Message-ID: <CAA4eK1KNGMqQbp7qkKjvVnbQVSR14pmg_WVqpaAzaKKSiN_zFQ@mail.gmail.com> (raw)
In-Reply-To: <TY4PR01MB1690715C2DD73955A5B8C1BD99452A@TY4PR01MB16907.jpnprd01.prod.outlook.com>
References: <[email protected]>
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On Mon, Mar 30, 2026 at 1:44 PM Zhijie Hou (Fujitsu)
<[email protected]> wrote:
>
> On Monday, March 30, 2026 2:33 PM Chao Li <[email protected]> wrote:
> > > On Mar 30, 2026, at 14:16, Nisha Moond <[email protected]>
> > wrote:
> > >
> > > On Fri, Mar 27, 2026 at 3:22 PM Chao Li <[email protected]> wrote:
> > > > This looks like a first-day bug introducing by ce0fdbf, so I think it’s worth
> > > > back-patching.
> > > >
> > > I tried reproducing the said bug on HEAD, but it doesn’t seem to exist
> > > in the current code.
> > >
> > > To hit the mentioned error, the subid has to be invalid -
> > >   if (!OidIsValid(subid) &&  <==
> > > And currently, the only path that uses an invalid subid is via
> > > heap_drop_with_catalog() :
> > > …
> > > /*
> > >   * Remove any associated relation synchronization states.
> > >   */
> > >  RemoveSubscriptionRel(InvalidOid, relid);
> > > …
> > >
> > > But here relid is always a valid OID (it's the table being dropped).
> > > The corresponding pg_class row is deleted after
> > > RemoveSubscriptionRel(), i.e. via a later call to
> > > DeleteRelationTuple(relid);
> > >
> > > It can only happen with a hypothetical future caller of
> > > RemoveSubscriptionRel(InvalidOid, InvalidOid). And in that case, using
> > > "subrel->srrelid" would be correct.
> > >
> > > So this doesn’t appear to be a real issue in the current code, and
> > > doesn’t look like a bug to fix now. IMO, if such a caller is added in
> > > the future, we can add a guard at that point.
> > >
> > > --
> > > Thanks,
> > > Nisha
> >
> > Hi Nisha,
> >
> > Thanks for your review.
> >
> > I think one current call site may have been overlooked. In DropSubscription(),
> > we have:
> > ```
> >     /* Remove any associated relation synchronization states. */
> >     RemoveSubscriptionRel(subid, InvalidOid);
> > ```
>
> This won't trigger the bug either, since it passes a valid subscription OID to
> the function, while the function only reports an error when an invalid OID is
> passed.
>
> >
> > I agree this is an edge-case bug and may be difficult to reproduce in practice.
> > But from the function’s semantics, it seems clear to me that the wrong
> > relation OID is used in the error detail, regardless of how easy it is to trigger
> > today.
>
> Since this is a public function, I think it should be OK to fix it as it's good
> to make the function future-proof anyway.
>

Even if it is exposed, it is not clear to me in which case one would
like to use it the way it can lead to a problem. I feel unless we have
some concrete case it may not be beneficial to change it.

-- 
With Regards,
Amit Kapila.

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