Re: jsonb concatenate operator's semantics seem questionable

Petr Jelinek wrote:
> On 20/05/15 01:38, Jim Nasby wrote:

> >If we get this wrong now, we'll be stuck with it forever. At a minimum I
> >think we should use anything other than || until we can figure this out.
> >That leaves || available for whichever case we decide on.
> 
> I am of strong opinion that concat should be shallow by default. Again it's
> how jquery works by default, it's how python's dict.update works and you can
> find this behavior in other languages as well when dealing with nested
> hashes. It's also how json would behave if you'd just did string
> concatenation (removing the outermost curly brackets) and parse it to json
> afterwards.
> 
> I think this whole discussion shows primarily that it's by far not
> universally agreed if concatenation of json should be shallow or deep by
> default and AFAICS this is true even in javascript world so we don't really
> have where to look for precedents.
> 
> Given the above I would vote to just provide the function and leave out the
> || operator for now.

+1 for providing just functions, not operators, for this JSON so-called
"concatenation".

But it is not really concatenation, is it?  This is more like a "merge"
operation.  I mean, if you told somebody that this operation is
concatenation  'xyz foo yxz' || 'bar' --> 'xyz bar yxz'

they would laugh at you pretty hard.  But that's precisely what is
happening here:

alvherre=# select jsonb '{"a": 1, "b": 2, "c": 3}' || '{"b": 4}';        ?column?         
--------------------------{"a": 1, "b": 4, "c": 3}
(1 fila)

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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