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From: Artur Formella <[email protected]>
To: Matthias van de Meent <[email protected]>
Cc: [email protected]
Subject: Re: Allowing additional commas between columns, and at the end of the SELECT clause
Date: Tue, 14 May 2024 00:26:50 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAEze2WhL_A9QO1xHQnEoYN1g5wsigqrL2+FLELcjFwaA-nP-Ug@mail.gmail.com>
References: <[email protected]>
	<CAEze2WhL_A9QO1xHQnEoYN1g5wsigqrL2+FLELcjFwaA-nP-Ug@mail.gmail.com>

On 13.05.2024 11:24, Matthias van de Meent wrote:
> On Mon, 13 May 2024 at 10:42, Artur Formella<[email protected]>  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.
Thank for your comment.
I meant commas are recommended at the end of the list. Sorry for the 
lack of precision.
Typescript has a popular directive "rules": { "trailing-comma": false } 
in the tslint.json file, which forces trailing commas. Popular Airbnb 
coding style require trailing commas by eslint 
(https://github.com/airbnb/javascript?tab=readme-ov-file#functions--signature-invocation-indentation).

> 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?
I don't know, I have a feeling that the queries are equivalent, but I 
don't know the mechanism.
> 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

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