Re: [HACKERS] [PATCH] Generic type subscripting

> On Wed, May 29, 2019 at 6:17 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
> st 29. 5. 2019 v 17:49 odesílatel Dmitry Dolgov <9erthalion6(at)gmail(dot)com> napsal:
>>
>> Rebase after pg_indent. Besides, off the list there was a suggestion that this
>> could be useful to accept more than one data type as a key for subscripting.
>> E.g. for jsonb it probably makes sense to understand both a simple key name and
>> jsonpath:
>>
>> jsonb['a'] and jsonb['$.a']
>>
>> While to implement it can be technically relatively straightforward I guess, I
>> wonder if there is any opinion about how valuable it could be and what it
>> should looks like from the syntax point of view (since I believe a user needs
>> to specify which type needs to be used).
>
>
> It is difficult decision - possibility to use jsonpath looks great, but
> necessity to cast every time is not friendly.

Thanks. Yes, I also wonder if it's possible to avoid type casting every time,
but other ideas seems syntactically equally not friendly.

> Probably there can be preferred type if subscripting is of unknown type.
> There can be similar rules to function's parameters.
>
> so jsonb['a'] -- key
> jsonb['$.a'] -- key
> jsonb['$.a'::jsonpath'] -- json path
>
> but it can be source of bad issues - so I think we don't need this feature in
> this moment. This feature can be implemented later, I think.

Yeah, I agree it's something that looks like a good potential improvement, not
now but in the future.