Re: SQL/JSON: functions

From: Erik Rijkers <er(at)xs4all(dot)nl>
To: Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>
Cc: Zhihong Yu <zyu(at)yugabyte(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Michael Paquier <michael(at)paquier(dot)xyz>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Andrew Alsup <bluesbreaker(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Oleg Bartunov <obartunov(at)postgrespro(dot)ru>, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: SQL/JSON: functions
Date: 2021-01-23 10:37:41
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On 2021-01-20 03:49, Nikita Glukhov wrote:

> [0001-Add-common-SQL-JSON-clauses-v52.patch.gz]
> [0002-SQL-JSON-constructors-v52.patch.gz]
> [0003-IS-JSON-predicate-v52.patch.gz]
> [0004-SQL-JSON-query-functions-v52.patch.gz]
> [0005-SQL-JSON-functions-for-json-type-v52.patch.gz]
> [0006-GUC-sql_json-v52.patch.gz]


I read through the file func.sgml (only that file) and put the
errors/peculiarities in the attached diff. (Small stuff; typos really)

Your patch includes a CREATE TABLE my_films + INSERT, to run the
examples against. I think this is a great idea and we should do it more

But, the table has a text-column to contain the subsequently inserted
json values. The insert runs fine but it turns out that some later
examples queries only run against a jsonb column. So I propose to
CREATE TABLE my_films (js text);
CREATE TABLE my_films (js jsonb);

This change is not yet included in the attached file. An alternative
would be to cast the text-column in the example queries as js::jsonb

I also noticed that some errors were different in the sgml file than 'in
the event':

SELECT JSON_QUERY(js, '$.favorites[*].kind' ERROR ON ERROR) FROM
(table 'my_films_jsonb' is the same as your 'my_films', but with js
as a jsonb column)

manual says: "ERROR: more than one SQL/JSON item"
in reality: "ERROR: JSON path expression in JSON_QUERY should return
singleton item without wrapper"
and: "HINT: use WITH WRAPPER clause to wrap SQL/JSON item
sequence into array"


Erik Rijkers

> --
> Nikita Glukhov
> Postgres Professional:
> The Russian Postgres Company

Attachment Content-Type Size
func.sgml.20210123.diff text/x-diff 7.5 KB

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