Re: Document aggregate functions better w.r.t. ORDER BY
| От | David G. Johnston |
|---|---|
| Тема | Re: Document aggregate functions better w.r.t. ORDER BY |
| Дата | |
| Msg-id | CAKFQuwY90Z-Wbe98oDfWS2WLucPQ+e5vXsCHfTOdssXvTyU0Ng@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Document aggregate functions better w.r.t. ORDER BY (Bruce Momjian <bruce@momjian.us>) |
| Ответы |
Re: Document aggregate functions better w.r.t. ORDER BY
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| Список | pgsql-hackers |
On Thu, Oct 26, 2023 at 2:56 PM Bruce Momjian <bruce@momjian.us> wrote:
On Wed, Oct 25, 2023 at 10:34:10PM -0700, David G. Johnston wrote:
> I would reword the existing note to be something like:
>
> The SQL Standard defines specific aggregates and their properties, including
> which of DISTINCT and/or ORDER BY is allowed. Due to the extensible nature of
> PostgreSQL it accepts either or both clauses for any aggregate.
Uh, is this something in my patch or somewhere else? I don't think
PostgreSQL extensible is an example of syntax flexibility.
Note
The ability to specify both DISTINCT and ORDER BY in an aggregate function is a PostgreSQL extension.
The ability to specify both DISTINCT and ORDER BY in an aggregate function is a PostgreSQL extension.
I am pointing out that the first sentence of the existing note above seems to be factually incorrect. I tried to make it correct - while explaining why we differ. Though in truth I'd probably rather just remove the note.
> We get enough complaints regarding "apparent ordering" that I would like to
> add:
>
> As a reminder, while some DISTINCT processing algorithms produce sorted output
> as a side-effect, only by specifying ORDER BY is the output order guaranteed.
Well, we need to create a new email thread for this and look at all the
areas is applies to since this is a much larger issue.
I was hoping to sneak this one in regardless of the bigger picture issues, since this specific combination is guaranteed to output ordered presently.
David J.
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