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From: Kirill Reshke <reshkekirill@gmail.com>
Date: Tue, 17 Mar 2026 18:24:26 +0500
Message-ID: <CALdSSPj1kTTQvmV3H3HMf5P3um8ybxoH3DaTPm+XgdYAur1Q4A@mail.gmail.com>
Subject: Re: BUG #19435: Error: "No relation entry for relid 2" Triggered by
 Complex Join with Self-Referencing Tables
To: Tender Wang <tndrwang@gmail.com>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, Fujii Masao <masao.fujii@gmail.com>, ammmkilo@163.com, 
	pgsql-bugs@lists.postgresql.org
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On Tue, 17 Mar 2026 at 18:20, Tender Wang <tndrwang@gmail.com> wrote:
>
> Tender Wang <tndrwang@gmail.com> =E4=BA=8E2026=E5=B9=B43=E6=9C=8817=E6=97=
=A5=E5=91=A8=E4=BA=8C 20:59=E5=86=99=E9=81=93=EF=BC=9A
> >
> > 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.
> > --
> (gdb) pgprint rinfo
> RestrictInfo [is_pushed_down=3Dfalse can_join=3Dfalse pseudoconstant=3Dfa=
lse
> has_clone=3Dtrue is_clone=3Dfalse leakproof=3Dfalse
> has_volatile=3DVOLATILITY_UNKNOWN security_level=3D0
>               num_base_rels=3D1 rinfo_serial=3D4 eval_cost=3D{startup =3D=
 -1,
> per_tuple =3D 0} norm_selec=3D-1 outer_selec=3D-1 outer_is_left=3Dfalse
> hashjoinoperator=3D0 left_bucketsize=3D-1
>               right_bucketsize=3D-1 left_mcvfreq=3D-1 right_mcvfreq=3D-1
> left_hasheqoperator=3D0 right_hasheqoperator=3D0]
> [clause] Var [varno=3D2 varattno=3D2 vartype=3D16
> varreturningtype=3DVAR_RETURNING_DEFAULT varnosyn=3D2 varattnosyn=3D2]
> [clause_relids] Bitmapset [3]
> [required_relids] Bitmapset [3 1]
> [incompatible_relids] Bitmapset [7 6]
> [outer_relids] Bitmapset [6 5 3]
>
> The above is the joininfo of the rtindex=3D1(tom0),  we can see that the
> required_relids is changed to [3 1], but the clause is still
> rtindex=3D2(varno=3D2).
> I guess the current logic in remove_self_join_rel() may forget to
> process the rinfo->clause.

Yes, it looks like your analysis is valid. Will you share a patch for
updating `clause` ?


--=20
Best regards,
Kirill Reshke