Re: Bug: var_is_nonnullable() gives wrong results for old/new in RETURNING

SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> 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