Re: row_to_json(), NULL values, and AS

[ Hi Tom! Hope you're doing well. ]

On Fri, Jun 15, 2018 at 7:53 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Oh! What is actually happening is
>
> (1) With no explicit alias, the column name of the sub-select's second
> output column is chosen to be "row_to_json".
>
> (2) That makes the outer query's notation row_to_json(x) ambiguous: it
> could be a function-syntax reference to the column x.row_to_json.
>
> (3) As it happens, the column interpretation is chosen when it's
> ambiguous (cf ParseComplexProjection).
>
> I'm a bit hesitant to muck with this behavior, given that it's stood
> for ~20 years. However, if we did want to touch it, maybe the right
> thing would be to give up the absolutist position that f(x) and x.f
> are exactly interchangeable. We could say instead that we prefer the
> function interpretation if function syntax is used, and the column
> interpretation if column syntax is used.

Interesting! Your proposed change seems quite reasonable to me.

Thanks for digging into it.

Neil