how to correctly cast json value to text?

Hi

po 3. 5. 2021 v 11:15 odesílatel Pavel Stehule <pavel.stehule@gmail.com>
napsal:

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

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.

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;
$function$

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

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

Some ideas about the name of this function?

CREATE OR REPLACE FUNCTION jsonscalar_to_text(jsonb)
RETURNS text AS $$
SELECT $1 #>> '{}'
$$ LANGUAGE sql;