Re: Allowing additional commas between columns, and at the end of the SELECT clause - Mailing list pgsql-hackers

On Mon, 13 May 2024 at 10:42, Artur Formella <artur.formella3@gmail.com> wrote:

Motivation:
Commas of this type are allowed in many programming languages, in some
it is even recommended to use them at the ends of lists or objects.

Single trailing commas are a feature that's more and more common in
languages, yes, but arbitrary excess commas is new to me. Could you
provide some examples of popular languages which have that, as I can't
think of any.

This is the first time I've heard of this `1 as dummy`.

dummy column is a popular way to end SELECT list on R&D phase to avoid the most common syntax error. This way you don't have to pay attention to commas.

SELECT <hacking /> , 1::int AS ignoreme FROM <hacking />

- simplifies query generators,
- the query is still deterministic,

What part of a query would (or would not) be deterministic? I don't
think I understand the potential concern here. Is it about whether the
statement can be parsed deterministically?

Bison doesn't report error or conflict.

I'd argue you better raise this with the standard committee if this
isn't compliant. I don't see enough added value to break standard
compliance here, especially when the standard may at some point allow
only a single trailing comma (and not arbitrarily many).


Do you expect `SELECT 1,,,,,,,` to have an equivalent query identifier
to `SELECT 1;` in pg_stat_statements? Why, or why not?

Overall, I don't think unlimited commas is a good feature. A trailing
comma in the select list would be less problematic, but I'd still want
to follow the standard first and foremost.

I will prepare a patch with trailing comma only tomorrow.

Thank you.

Artur