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From: Tender Wang <tndrwang@gmail.com>
Date: Fri, 10 Apr 2026 09:29:48 +0800
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 <CAHewXN=9mf6NCeHE=7jUVhM_Ur=oW8R7hgfQwcvyWCSLC8VERw@mail.gmail.com>
Subject: Re: Bug: var_is_nonnullable() gives wrong results for old/new in
 RETURNING
To: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Richard Guo <guofenglinux@gmail.com>
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SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> =E4=BA=8E2026=E5=B9=B4=
4=E6=9C=8810=E6=97=A5=E5=91=A8=E4=BA=94 02:43=E5=86=99=E9=81=93=EF=BC=9A
>
> Hi hackers,
>
> It appears the optimizer incorrectly simplifies old.<col> IS NULL to FALS=
E in RETURNING clauses when the underlying column has a NOT NULL constraint=
.
>
> The issue is that var_is_nonnullable() in clauses.c doesn't check Var.var=
returningtype. It sees a NOT NULL column and concludes the Var can never be=
 NULL.
> But this assumption is wrong for old.* and new.* references. Because the =
old tuple doesn't exist on INSERT, and the new tuple doesn't exist on DELET=
E
> I am not super familiar with this area, so I attempted to fix this as in =
the patch attached.

Yes,  the current var_is_nonnullable() ignores this case.  The
attached patch seems ok to me.

Add Richard to the cc list. He may know more about this.
--=20
Thanks,
Tender Wang