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From: Tender Wang <[email protected]>
To: SATYANARAYANA NARLAPURAM <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Richard Guo <[email protected]>
Subject: Re: Bug: var_is_nonnullable() gives wrong results for old/new in RETURNING
Date: Fri, 10 Apr 2026 09:29:48 +0800
Message-ID: <CAHewXN=9mf6NCeHE=7jUVhM_Ur=oW8R7hgfQwcvyWCSLC8VERw@mail.gmail.com> (raw)
In-Reply-To: <CAHg+QDfaAipL6YzOq2H=gAhKBbcUTYmfbAv+W1zueOfRKH43FQ@mail.gmail.com>
References: <CAHg+QDfaAipL6YzOq2H=gAhKBbcUTYmfbAv+W1zueOfRKH43FQ@mail.gmail.com>

SATYANARAYANA NARLAPURAM <[email protected]> 于2026年4月10日周五 02:43写道：
>
> Hi hackers,
>
> It appears the optimizer incorrectly simplifies old.<col> IS NULL to FALSE 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.varreturningtype. 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 DELETE
> 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.
-- 
Thanks,
Tender Wang

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