Re: Minor suggestions for docs regarding json_table

On Fri, Feb 14, 2025 at 3:00 AM Amit Langote <amitlangote09(at)gmail(dot)com>
wrote:

> On Sun, Feb 9, 2025 at 12:59 AM Robert Treat <rob(at)xzilla(dot)net> wrote:
> > So, how does this thing get used? AFAIK there is no way to reference
> > these aliases at the query level, instead they only show up within
> > EXPLAIN VERBOSE output. Below is said output, where you'll see that
> > the aliases I provided show up at their corresponding levels, but the
> > level for "movies", which was unaliased, shows up with the system
> > generated "json_table_path_0".
> >
> > Table Function Scan on "json_table" (cost=0.01..1.01 rows=100 width=144)
> > Output: user_id, movie_id, mname, director, book_id, bname,
> > author_id, writer_name
> > Table Function Call: JSON_TABLE('{"favorites": [{"books": [{"name":
> > "Mystery", "authors": [{"name": "Brown Dan"}]}, {"name": "Wonder",
> > "authors": [{"name": "Jun Murakami"}, {"name": "Craig Doe"}]}],
> > "movies": [{"name": "One", "director": "John Doe"}, {"name": "Two",
> > "director": "Don Joe"}]}]}'::jsonb, '$."favorites"[*]' AS fav COLUMNS
> > (user_id FOR ORDINALITY, NESTED PATH '$."movies"[*]' AS
> > json_table_path_0 COLUMNS (movie_id FOR ORDINALITY, mname text PATH
> > '$."name"', director text PATH '$."director"'), NESTED PATH
> > '$."books"[*]' AS book COLUMNS (book_id FOR ORDINALITY, bname text
> > PATH '$."name"', NESTED PATH '$."authors"[*]' AS writer COLUMNS
> > (author_id FOR ORDINALITY, writer_name text PATH '$."name"'))))
> > Query Identifier: -8600959643289807018
> > (4 rows)
> >
> > Given the relative obscurity of this (and the difficulty I had in
> > remembering it), I do think it warrants an extra line in the docs.
> > I've attached a patch with some suggested wording and the previous two
> > fixes.
>
> The path names are not particularly useful in queries, meaning they
> don’t serve a purpose in path expressions. However, they will be
> needed when the PLAN clause is supported [1].
>

<snip>

>
>
Given this, I think we should leave the path name documentation as it
> is for now and address it, if needed, as part of the patch for the
> PLAN clause. I'll go ahead and push your other fixes as in the
> attached patch.
>
>
Ah, thanks for the heads up. Reasoning makes sense to me / patch looks
good. Thanks!

Robert Treat
https://xzilla.net