Re: BUG #17477: A crash bug in transformValuesClause()

On Tue, May 10, 2022 at 2:20 AM Jonathan S. Katz <jkatz@postgresql.org> wrote:
>
> On 5/9/22 11:25 AM, Tom Lane wrote:
> > Masahiko Sawada <sawada.mshk@gmail.com> writes:
> >> It seems like transformValuesClause() cannot handle properly the value
> >> clause having a relation that has an empty column. Should we raise an
> >> error in this case?
> >
> > Given that we try to support zero-column relations, I'm not sure why
> > we'd insist on disallowing zero-column VALUES.  I think the problem
> > is that the code in transformValuesClause needs to be tweaked to
> > make that work.  The attached quick hack seems to do the trick.
>
> Agree with the reasoning.
>
> Confirmed reproducing the crash and that this fixes it. I did a short
> double-take on the error message:
>
>         ERROR:  subquery must return only one column
>
> but it is accurate, given this is what the subquery must do, and zero !=
> one.

Agreed. I've also confirmed that the patch fixes this issue and passed
the regression tests.

Regards,

--
Masahiko Sawada
EDB:  https://www.enterprisedb.com/