Re: Tackling JsonPath support

On Mon, Nov 28, 2016 at 11:23 AM, Nico Williams <nico(at)cryptonector(dot)com>
wrote:
...

> JSON Path is not expressive enough (last I looked) and can be mapped
> onto jq if need be anyways.
>

​Hi Nico,

Could you please clarify what you mean by "not expressive enough"?

I ask because I've been struggling to identify clear requirements for the
json-path functionality I'm trying to provide. It sounds like perhaps you
have something concrete in mind.

Since I myself have no need currently for this functionality, I'm left
guessing about hypothetical users of it.​ My current mental model is:

(a) Backend web developers. AFAICT, their community has mostly settled on
the syntax/semantics proposed by Stefan Groessner. It would probably be
unkind for PG's implementation to deviate from that without a good reason.

(b) PG hackers who will eventually implement the ISO SQL standard
operators. In the standards-committee meeting notes I've seen, it seemed
to me that they were planning to define some operators in terms of
json-path expression. So it would probably be good if whatever json-path
function I implement turns out to comply with that standard, so that the
PG-hackers can use it as a building block for their work.

(c) Pavel. (I'm still somewhat unclear on what has him interested in this,
and what his specific constraints are.)

- Christian