Re: [HACKERS] [PATCH] Generic type subscripting

> On Thu, Dec 17, 2020 at 01:49:17PM -0500, Tom Lane wrote:
> Dmitry Dolgov <9erthalion6@gmail.com> writes:
> > While rebasing the jsonb patch I found out that the current subscripting
> > assignment implementation in transformAssignmentIndirection always
> > coerce the value to be assigned to the type which subscripting result
> > suppose to have (refrestype). For arrays it's fine, since those two
> > indeed must be the same, but for jsonb (and for hstore I guess too) the
> > result of subscripting is always jsonb (well, text type) and the
> > assigned value could be of some other type. This leads to assigning
> > everything converted to text.
>
> So ... what's the problem with that?  Seems like what you should put
> in and what you should get out should be the same type.
>
> We can certainly reconsider the API for the parsing hook if there's
> really a good reason for these to be different types, but it seems
> like that would just be encouraging poor design.

To be more specific, this is the current behaviour (an example from the
tests) and it doesn't seem right:

    =# update test_jsonb_subscript
       set test_json['a'] = 3 where id = 1;

    UPDATE 1

    =# select jsonb_typeof(test_json->'a')
       from test_jsonb_subscript where id = 1;

     jsonb_typeof
     --------------
      string

    =# update test_jsonb_subscript
       set test_json = jsonb_set(test_json, '{a}', '3') where id = 1;

    UPDATE 1
    =# select jsonb_typeof(test_json->'a')
       from test_jsonb_subscript where id = 1;

     jsonb_typeof
     --------------
      number