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From: Tender Wang <tndrwang@gmail.com>
Date: Tue, 17 Mar 2026 20:59:04 +0800
Message-ID: <CAHewXNmU3E0oXLgvoOtXw7kfTiAZsKu8La_hQ=pyScgxvP45iw@mail.gmail.com>
Subject: Re: BUG #19435: Error: "No relation entry for relid 2" Triggered by
 Complex Join with Self-Referencing Tables
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Fujii Masao <masao.fujii@gmail.com>, ammmkilo@163.com, 
	pgsql-bugs@lists.postgresql.org
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Alexander Korotkov <aekorotkov@gmail.com> =E4=BA=8E2026=E5=B9=B43=E6=9C=881=
7=E6=97=A5=E5=91=A8=E4=BA=8C 20:26=E5=86=99=E9=81=93=EF=BC=9A
>
> On Tue, Mar 17, 2026 at 2:14=E2=80=AFPM Fujii Masao <masao.fujii@gmail.co=
m> wrote:
> >
> > On Tue, Mar 17, 2026 at 7:34=E2=80=AFPM PG Bug reporting form
> > <noreply@postgresql.org> wrote:
> > >
> > > The following bug has been logged on the website:
> > >
> > > Bug reference:      19435
> > > Logged by:          Hang ammmkilo
> > > Email address:      ammmkilo@163.com
> > > PostgreSQL version: 18.3
> > > Operating system:   Ubuntu 22.04
> > > Description:
> > >
> > > A user encountered an error when attempting to execute a query involv=
ing
> > > multiple RIGHT JOIN operations and a NATURAL JOIN on the same table
> > > (pg_table_a). The error message returned was:
> > > [XX000]ERROR: no relation entry for relid 2
> > > This error seems to be an internal one and should not be triggered by=
 users.
> > > It might be a bug.
> > > ```sql
> > > DROP TABLE IF EXISTS pg_table_a;
> > >
> > > CREATE TABLE pg_table_a (
> > >     id INTEGER PRIMARY KEY,
> > >     col_bool BOOLEAN
> > > );
> > >
> > > INSERT INTO pg_table_a (id, col_bool)
> > > VALUES (5, TRUE);
> > >
> > > SELECT  1 AS c1
> > > FROM (
> > >     pg_table_a AS tom0
> > >     RIGHT JOIN (
> > >         (pg_table_a AS tom1 NATURAL JOIN pg_table_a AS tom2)
> > >         RIGHT JOIN pg_table_a AS tom3
> > >         ON tom1.col_bool IS NOT NULL
> > >     )
> > >     ON tom1.col_bool
> > > );
> > > ```
> >
> > Thanks for the report!
> >
> > I was able to reproduce this issue on the master. git bisect that I ran=
 pointed
> > to commit fc069a3a631 as the likely cause. So I've CC'd its committer,
> > Alexander, on this thread.
>
> Thank you for adding me to the thread.  I'm lookin at this.

The error was reported in rebuild_joinclause_attr_needed() when
processing Relid =3D 1(rtindex =3D1),
When processing its joininfo" ON tom1.col_bool IS NOT NULL",
(gdb) pgprint rinfo->clause
Var [varno=3D2 varattno=3D2 vartype=3D16
varreturningtype=3DVAR_RETURNING_DEFAULT varnosyn=3D2 varattnosyn=3D2]

The varno=3D2, rtindex=3D2(tom1) has been removed. In
add_vars_to_attr_needed(), to find the base_rel, but the
root->simple_rel_array[2] is NULL.
So the error is reporting.
It seems the joininfo should be replaced by rtindex =3D 3, because the
rtindex=3D2 would be removed.
--=20
Thanks,
Tender Wang