Обсуждение: how to correctly cast json value to text?
Hi
I am testing a new subscripting interface for jsonb, and I found one issue.
DO $$
DECLARE v jsonb;
BEGIN
v['a'] = '"Ahoj"';
RAISE NOTICE '%', v['a'];
END;
$$;
NOTICE: "Ahoj"
DO
DECLARE v jsonb;
BEGIN
v['a'] = '"Ahoj"';
RAISE NOTICE '%', v['a'];
END;
$$;
NOTICE: "Ahoj"
DO
When I use this interface for reading, the jsonb type is returned. What is the correct way for casting from jsonb text to text value? I would not double quotes inside the result. Cast to text doesn't help. For operator API we can use "->>" symbol. But we have nothing similar for subscript API.
Regards
Pavel
Hi
po 3. 5. 2021 v 11:15 odesílatel Pavel Stehule <pavel.stehule@gmail.com> napsal:
HiI am testing a new subscripting interface for jsonb, and I found one issue.DO $$
DECLARE v jsonb;
BEGIN
v['a'] = '"Ahoj"';
RAISE NOTICE '%', v['a'];
END;
$$;
NOTICE: "Ahoj"
DOWhen I use this interface for reading, the jsonb type is returned. What is the correct way for casting from jsonb text to text value? I would not double quotes inside the result. Cast to text doesn't help. For operator API we can use "->>" symbol. But we have nothing similar for subscript API.
now I need function like
CREATE OR REPLACE FUNCTION public.value_to_text(jsonb)
RETURNS text
LANGUAGE plpgsql
IMMUTABLE
AS $function$
DECLARE x jsonb;
BEGIN
x['x'] = $1;
RETURN x->>'x';
END;
$function$
RETURNS text
LANGUAGE plpgsql
IMMUTABLE
AS $function$
DECLARE x jsonb;
BEGIN
x['x'] = $1;
RETURN x->>'x';
END;
$function$
DO $$
DECLARE v jsonb;
BEGIN
-- hodnota musi byt validni json
v['a'] = '"Ahoj"';
RAISE NOTICE '%', value_to_text(v['a']);
END;
$$;
NOTICE: Ahoj
DO
DECLARE v jsonb;
BEGIN
-- hodnota musi byt validni json
v['a'] = '"Ahoj"';
RAISE NOTICE '%', value_to_text(v['a']);
END;
$$;
NOTICE: Ahoj
DO
Is it possible to do this with built functionality?
I miss the cast function for json scalar string value to string.
Regards
Pavel
RegardsPavel
On Mon, May 3, 2021 at 12:24 PM Pavel Stehule <pavel.stehule@gmail.com> wrote:
Is it possible to do this with built functionality?I miss the cast function for json scalar string value to string.
#>>'{}'
.m
po 3. 5. 2021 v 11:26 odesílatel Marko Tiikkaja <marko@joh.to> napsal:
On Mon, May 3, 2021 at 12:24 PM Pavel Stehule <pavel.stehule@gmail.com> wrote:Is it possible to do this with built functionality?I miss the cast function for json scalar string value to string.#>>'{}'
It is working. Thank you. But this syntax is a little bit scary. Maybe we can introduce some functions for this case. Until to pg 14 this functionality was not necessary, but now it can be nice to have it.
DO $$
DECLARE v jsonb;
BEGIN
-- hodnota musi byt validni json
v['a'] = '"Ahoj"';
RAISE NOTICE '%', v['a'] #>> '{}';
END;
$$;
NOTICE: Ahoj
DO
DECLARE v jsonb;
BEGIN
-- hodnota musi byt validni json
v['a'] = '"Ahoj"';
RAISE NOTICE '%', v['a'] #>> '{}';
END;
$$;
NOTICE: Ahoj
DO
Some ideas about the name of this function?
CREATE OR REPLACE FUNCTION jsonscalar_to_text(jsonb)
RETURNS text AS $$
SELECT $1 #>> '{}'
$$ LANGUAGE sql;
.m