Re: SQL/JSON path issues/questions

On Fri, Jun 28, 2019 at 9:01 AM Oleg Bartunov <obartunov(at)postgrespro(dot)ru> wrote:
> On Fri, Jun 28, 2019 at 8:10 AM Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
> >
> > On 2019-Jun-28, Alexander Korotkov wrote:
> >
> > > On Tue, Jun 25, 2019 at 6:38 PM Liudmila Mantrova
> > > <l(dot)mantrova(at)postgrespro(dot)ru> wrote:
> > > > Thank you for the catch! Please see the modified version of patch 0004
> > > > attached.
> > >
> > > I tried to review and revise the part related to filters, but I failed
> > > because I don't understand the notions used in the documentation.
> > >
> > > What is the difference between filter expression and filter condition?
> > > I can guess that filter expression contains question mark,
> > > parentheses and filter condition inside. But this sentence is in
> > > contradiction with my guess: "A filter expression must be enclosed in
> > > parentheses and preceded by a question mark". So, filter expression
> > > is inside the parentheses. Then what is filter condition? The same?
> >
> > The SQL standard defines "JSON filter expressions" (in 9.39 of the 2016
> > edition). It does not use either term "filter condition" nor bare
> > "filter"; it uses "JSON path predicate" which is the part of the JSON
> > filter expression that is preceded by the question mark and enclosed by
> > parens.
>
> Yes, this is what I used in my talk
> http://www.sai.msu.su/~megera/postgres/talks/jsonpath-ibiza-2019.pdf
>
> >
> > Maybe we should stick with the standard terminology ...
>
> Sure.

+1

> As for the jsonpath documentation, I think we should remember, that
> jsonpath is a part of SQL/JSON, and in the following releases we will
> expand documentation to include SQL/JSON functions, so I suggest to
> have one chapter SQL/JSON with following structure:
> 1. Introduction
> 1.1 SQL/JSON data model
> 1.2 SQL/JSON path language
> 1.3 <SQL/JSON functions> -- to be added
> 2. PostgreSQL implementation
> 2.1 jsonpath data type -- link from json data types
> 2.2 jsonpath functions and operators -- link from functions
> 2.3 Indexing
>
> I plan to work on a separate chapter "JSON handling in PostgreSQL" for
> PG13, which includes
> JSON(b) data types, functions, indexing and SQL/JSON.

It would be great if you manage to do this.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company