Re: Please provide examples of rows from
| От | David G. Johnston |
|---|---|
| Тема | Re: Please provide examples of rows from |
| Дата | |
| Msg-id | CAKFQuwbBDr22KJRyJQRECO_XU6cyouwz3ocn0Tv4JgG4Gm5hMQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Please provide examples of rows from (Bruce Momjian <bruce@momjian.us>) |
| Ответы |
Re: Please provide examples of rows from
Re: Please provide examples of rows from |
| Список | pgsql-docs |
On Thu, Sep 3, 2020 at 6:46 PM Bruce Momjian <bruce@momjian.us> wrote:
On Wed, Apr 8, 2020 at 09:50:44PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/12/queries-table-expressions.html
> Description:
>
> The explanation of ROWS FROM is fairly terse and no examples are given.
>
> As it is essentially impossible to usefully search for this phrase, it would
> be helpful if at least a few examples were given.
Looking at this suggestion, this was all I could think of:
SELECT * FROM ROWS FROM (GENERATE_SERIES(1,10), GENERATE_SERIES(1, 15));
generate_series | generate_series
-----------------+-----------------
1 | 1
2 | 2
3 | 3
4 | 4
5 | 5
6 | 6
7 | 7
8 | 8
9 | 9
10 | 10
(null) | 11
(null) | 12
(null) | 13
(null) | 14
(null) | 15
The issue with adding an example is that it is hard to do something
simple and have it illustrate anything. Does this help?
That documents one of the two variants - and incorporating the column alias feature seems worthwhile for the chosen example. I do think this is worth adding.
The more complicated one is the second:
ROWS FROM( ... function_call AS (column_definition [, ... ]) [, ... ] )
First, what's with the first set of "..."? It doesn't appear in the reference documentation.
I was looking at the "Queries" doc comment a little bit ago and am wondering if there is some principle by which we would decide to place any new examples in this section versus the examples part of the SELECT reference section?
I would note that part of the confusion probably stems from not defining "column definition" in this chapter. It probably could be defined more prominently in the SELECT reference as well.
Basically, aliases outside the ROWS FROM, column definitions within, unless there is only a single "record" returning function involved (and without ORDINALITY) in which case the external aliases can be instead a complete column definition.
For the simple solution to the complaint I would thus suggest three examples, but added to the SELECT reference, covering those three situations (mutli-typed-aliased, multi-record, single-rows-from-record-using-outside-columndef), and pointing the user to the SELECT reference for said examples. That would be in addition to the one example (another multi-typed-aliased) above being added to the queries section.
A more involved patch would need, IMO, some structure to make the queries section sufficient but less complex while relegating much of the complexity to the reference section. That seems to be doing a better job describing this reality presently anyway.
David J.
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