Re: group by true now errors with non-integer constant in GROUP BY

On Tue, 29 Aug 2023 at 13:02, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > I had a look on dbfiddle and I see that MySQL 8.0 and SQLlite all
> > allow GROUP BY true.
>
> What do they do with GROUP BY 1, or GROUP BY 10000, or GROUP BY 1.0 ?

All treat only integer constants as column references. Out-of-range
integer values are reported as errors. Other const types appear to be
treated as expressions rather than column references.

> BTW, I poked around and couldn't find anything explaining this
> fine point in the SGML docs, although the comments in
> findTargetlistEntrySQL92 are clear about it. If we do anything
> at all here, I think that ought to include documenting the behavior
> more clearly (and I'm curious to see how you'd propose to explain
> the behavior you want to users).

The rule and how to explain it seems fairly simple to me. Integer
constants are treated as column references to their corresponding
1-based position in the SELECT clause. Anything else is treated as an
expression.

David