public inbox for [email protected]  

help / color / mirror / Atom feed

From: Dagfinn Ilmari Mannsåker <[email protected]>
To: Tom Lane <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Artur Formella <[email protected]>
Cc: [email protected]
Subject: Re: Allowing additional commas between columns, and at the end of the SELECT clause
Date: Mon, 13 May 2024 17:35:42 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<CAEze2WhL_A9QO1xHQnEoYN1g5wsigqrL2+FLELcjFwaA-nP-Ug@mail.gmail.com>
	<[email protected]>
	<[email protected]>

Tom Lane <[email protected]> writes:

> =?utf-8?Q?Dagfinn_Ilmari_Manns=C3=A5ker?= <[email protected]> writes:
>> Matthias van de Meent <[email protected]> writes:
>>> 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.
>
>> The only one I can think of is Perl, which I'm not sure counts as
>> popular any more.  JavaScript allows consecutive commas in array
>> literals, but they're not no-ops, they create empty array slots:
>
> I'm fairly down on this idea for SQL, because I think it creates
> ambiguity for the ROW() constructor syntax.  That is:
>
> 	(x,y) is understood to be shorthand for ROW(x,y)
>
> 	(x) is not ROW(x), it's just x
>
> 	(x,) means what?

Python has a similar issue: (x, y) is a tuple, but (x) is just x, and
they use the trailing comma to disambiguate, so (x,) creates a
single-item tuple.  AFAIK it's the only place where the trailing comma
is significant.

> I realize the original proposal intended to restrict the legality of
> excess commas to only a couple of places, but to me that just flags
> it as a kluge.  ROW(...) ought to work pretty much the same as a
> SELECT list.

Yeah, a more principled approach would be to not special-case target
lists, but to allow one (and only one) trailing comma everywhere:
select, order by, group by, array constructors, row constructors,
everything that looks like a function call, etc.

> As already mentioned, if you can get some variant of this through the
> SQL standards process, we'll probably adopt it.  But I doubt that we
> want to get out front of the committee in this area.

Agreed.

> 			regards, tom lane

- ilmari

view thread (5+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected]
  Subject: Re: Allowing additional commas between columns, and at the end of the SELECT clause
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox