Re: [HACKERS] [PATCH] Generic type subscripting

On Tue, Mar 6, 2018 at 6:21 PM, Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:

>
> One more small update after fd1a421fe6 in attachments.
>

Before looking at the code I have a few comments about documentation:

in json.sgml:

+-- Extract value by key
+SELECT ('{"a": 1}'::jsonb)['a'];

What is the result of running this query? What is the resulting data type?

+-- Extract nested value by key path
+SELECT ('{"a": {"b": {"c": 1}}}'::jsonb)['a']['b']['c'];
+
+-- Extract element by index
+SELECT ('[1, "2", null]'::jsonb)['1'];

What is the result here? Why subscript is a string and not a number? Are
subscription indexes 0- or 1-based?

+-- Update value by key
+UPDATE table_name set jsonb_field['key'] = 1;
+
+-- Select records using where clause with subscripting
+SELECT * from table_name where jsonb_field['key'] = '"value"';

Please capitalize: SET, FROM, WHERE.

Use of double quotes around "value" requires some explanation, I think.
Should the user expect that a suitable index is used by the query planner
for this query?

In other words, I would like to see this part of documentation to be
extended beyond just showcasing the syntax.

Regards,
--
Oleksandr "Alex" Shulgin | Database Engineer | Zalando SE | Tel: +49 176
127-59-707