Обсуждение: 8.14.5 jsonb subscripting

On Tue, 2024-04-09 at 09:31 +0000, PG Doc comments form wrote:
> Page: https://www.postgresql.org/docs/16/datatype-json.html
>
> Using subscripts with square brackets is not supported, one must use -> or
> #> operators
> The given examples result in error:
>
> SELECT ('{"a": 1}'::jsonb)['a'];
>
> -- Extract nested object value by key path
> SELECT ('{"a": {"b": {"c": 1}}}'::jsonb)['a']['b']['c'];
>
> -- Extract array element by index
> SELECT ('[1, "2", null]'::jsonb)[1];

You must be using an old PostgreSQL version where that is not yet supported.

Yours,
Laurenz Albe

I am running on AWS RDS - it says engine version 12.17 i thought that was the postgres version. If so, the [] subscripting should be supported according to docs.

Arne

tir. 9. apr. 2024 kl. 13:16 skrev Laurenz Albe <laurenz.albe@cybertec.at>:

On Tue, 2024-04-09 at 09:31 +0000, PG Doc comments form wrote:
> Page: https://www.postgresql.org/docs/16/datatype-json.html
>
> Using subscripts with square brackets is not supported, one must use -> or
> #> operators
> The given examples result in error:
>
> SELECT ('{"a": 1}'::jsonb)['a'];
>
> -- Extract nested object value by key path
> SELECT ('{"a": {"b": {"c": 1}}}'::jsonb)['a']['b']['c'];
>
> -- Extract array element by index
> SELECT ('[1, "2", null]'::jsonb)[1];

You must be using an old PostgreSQL version where that is not yet supported.

Yours,
Laurenz Albe

Arne Sommerfelt <arne.sommerfelt@gmail.com> writes:
> I am running on AWS RDS - it says engine version 12.17 i thought that was
> the postgres version. If so, the [] subscripting should be supported
> according to docs.

According to what docs?  Generic subscripting was added in v14.

                        regards, tom lane

tir. 9. apr. 2024 kl. 16:00 skrev Tom Lane <tgl@sss.pgh.pa.us>:

Arne Sommerfelt <arne.sommerfelt@gmail.com> writes:
> I am running on AWS RDS - it says engine version 12.17 i thought that was
> the postgres version. If so, the [] subscripting should be supported
> according to docs.

According to what docs?  Generic subscripting was added in v14.

                        regards, tom lane

> On 9 Apr 2024, at 16:02, Arne Sommerfelt <arne.sommerfelt@gmail.com> wrote:

> <image.png>

Thats the documentation for v16, not the version you are running.

--
Daniel Gustafsson

> On 9 Apr 2024, at 16:04, Arne Sommerfelt <arne.sommerfelt@gmail.com> wrote:
>
> 12 is in the list of supported versions at the top of chapter 8.14. And the non-working examples is in subsection 8.14.5

I think you've misunderstood the header of the page.  This is the documentation
you should be reading for your version if Postgres:

        https://www.postgresql.org/docs/12/index.html

--
Daniel Gustafsson

Arne Sommerfelt <arne.sommerfelt@gmail.com> writes:
> Thank you!  When googling it is easy to end up with latest docs,
> unfortunately

That's actually good news --- it used to be that Google would
tend to steer people to very ancient versions of our docs.
Sounds like the SEO work that we've done is paying off.

However, if you're running a moderately old PG version, you need
to make use of the links at the top of the page to go to the
equivalent page in the older version's docs.

                        regards, tom lane