plpgsql extract array before loop on it's elements - json

Question

I am trying to create a plpg function taking as parameter :
[{'id_product': 100000158, 'd_price': '7,75'}, {'id_product': 100000339, 'd_price': '9,76'}]
Or maybe :
{'products': [{'id_product': 100000158, 'd_price': '7,75'}, {'id_product': 100000339, 'd_price': '9,76'}]}
Can't tell the best approach yet.
I want to transform this jsonb object or string to an array so I can loop on it.
The idea is to loop en every {'id_product': xxxxxxxxx, 'd_price': 'xxxxx'} so I if values are the same in a table.
What's the most optimal way to do this ?
I am still playing with jsonb functions.

Answer 1

You can create a function containing JSONB_POPULATE_RECORDSET() function
CREATE OR REPLACE FUNCTION fn_extract_elements( i_jsonb JSONB )
RETURNS TABLE (o_product VARCHAR(500), o_price VARCHAR(500))
AS $BODY$
BEGIN
RETURN QUERY
WITH tab AS
(
SELECT *
FROM JSONB_POPULATE_RECORDSET(NULL::record,i_jsonb )
AS tab(id_product VARCHAR(500), d_price VARCHAR(500))
)
SELECT *
FROM tab;
END
$BODY$
LANGUAGE plpgsql;
and invoke in such a way that
SELECT *
FROM fn_extract_elements(
'[{"id_product": "100000158", "d_price": "7,75"},
{"id_product": "100000339", "d_price": "9,76"}]'
);
o_product o_price
100000158 7,75
100000339 9,76
Demo

Answer 2

Here is a solution for those who might want to do something similar :
I changed the input to something like : {0: [100000158, 7.76], 1: [100000339, 9.76]}
And function :
CREATE OR REPLACE FUNCTION public.check_d_price(
p_products jsonb)
RETURNS jsonb
LANGUAGE 'plpgsql'
COST 100
VOLATILE PARALLEL UNSAFE
AS $BODY$
DECLARE
_key varchar;
_real_price NUMERIC;
_bad_price jsonb;
BEGIN
FOR _key IN (
SELECT jsonb_object_keys(p_products)
)
LOOP
SELECT ei.price INTO _real_price FROM product pr JOIN ecom_input ei ON (pr.ecom_id,pr.sku) = (ei.ecom_id,ei.sku_supplier) WHERE pr.id = (p_products->_key->>0)::INT;
IF _real_price <> (p_products->_key->>1)::NUMERIC THEN
_bad_price = COALESCE(_bad_price,'{}'::jsonb) || jsonb_build_object((p_products->_key->>0)::TEXT,
jsonb_build_object('d_price', p_products->_key->>1,'new_price', _real_price));
END IF;
END LOOP;
RETURN _bad_price;
END;
$BODY$;