Re: SQL/JSON path issues/questions - Mailing list pgsql-hackers

From Oleg Bartunov
Subject Re: SQL/JSON path issues/questions
Date
Msg-id CAF4Au4zH=t=x02A8kndYW=fV+5yPj=r55yWSZbcHt9PY7FYHyQ@mail.gmail.com
Whole thread Raw
In response to Re: SQL/JSON path issues/questions  (Alvaro Herrera <alvherre@2ndquadrant.com>)
Responses Re: SQL/JSON path issues/questions
List pgsql-hackers
On Fri, Jun 28, 2019 at 8:10 AM Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
>
> On 2019-Jun-28, Alexander Korotkov wrote:
>
> > On Tue, Jun 25, 2019 at 6:38 PM Liudmila Mantrova
> > <l.mantrova@postgrespro.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.

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.

>
> --
> Álvaro Herrera                https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
>


--
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