Re: jsonb concatenate operator's semantics seem questionable

> creates the specified path if it does not exist. Does it?

No, jsonb_replace() doesn't create an element, if it doesn't exist. I
think, otherwise it can be confusing, so probably jsonb_add() may be more
appropriate (and, actually, this function was already mentioned in previous
discussions).

On 18 May 2015 at 22:57, Ryan Pedela <rpedela(at)datalanche(dot)com> wrote:

> On Mon, May 18, 2015 at 8:41 AM, Ryan Pedela <rpedela(at)datalanche(dot)com>
> wrote:
>
>> On Sun, May 17, 2015 at 9:41 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
>>
>> Is there a particular reason why "+" makes more sense as "shallow
>>> concatination" and "||" makes more sense as "deep concatination"? Like,
>>> something in JS or other client languages which would make that
>>> preference make more sense to users?
>>>
>>
>> As someone who uses JSON day-to-day in Javascript and Python, I
>> personally don't think || or + matters much. Python uses json.loads() for
>> JSON concat and you have use a 3rd-party library in Javascript if you want
>> that functionality such as JQuery.extends(). I agree with Peter that we
>> need deep concatenation, but I don't think there is any standard for the
>> operator. I think the word "shallow" should be added to the docs though.
>>
>> What is far more important than shallow or deep concatenation for the
>> document database use case is being able to delete or replace/update a
>> specific, nested path in the JSON object. It looks like that is possible
>> with the minus operator and jsonb_replace(). This is great, however it took
>> me awhile to figure out the path syntax. I think adding a paragraph to the
>> docs explaining the path syntax would help.
>>
>
> Having looked at this more, I think I understand the problem Peter has
> identified and it is a significant usability problem in my opinion. I think
> the word "concatenate" has confused me because I think of it as a
> higher-level operation when I want to merge two, large JSON objects which
> isn't a very common operation, at least for me. What is absolutely required
> for the document database use case is the following:
>
> 1. Get element at any arbitrary path. ( #> operator )
> 2. Delete any arbitrary path. ( minus operator )
> 3. Replace/update element at any arbitrary path. ( jsonb_replace )
> 4. Add element to any arbitrary path. ( ? )
>
> It is #4 that does not seem to exist unless jsonb_replace() creates the
> specified path if it does not exist. Does it? I am not currently at my desk
> to test it myself.
>
> If not, deep concatenation would solve this problem, but I can also see
> another solution. Use + for shallow concatenation since it really means
> "add element to top-level path" as Peter suggests. Then add another
> function: jsonb_add( target jsonb, path text[], new jsonb ) to add element
> at any arbitrary path. Then leave || for deep concatenation in 9.6 or
> whenever.
>
> If jsonb_replace() satisfies #4 then I think everything is fine. Without
> #4 however, jsonb would remain an incomplete document database solution in
> my opinion.
>
> Thanks,
> Ryan Pedela
>
>