CREATE TABLE a (a_id int PRIMARY KEY, a text);
INSERT INTO a VALUES (1, 'foo'), (2, 'bar');

TABLE a;

DO $$
DECLARE
r record;
j jsonb;

BEGIN

FOR r IN SELECT * FROM a
LOOP

  SELECT row_to_json(r) INTO j;
  RAISE info '%', j;

END LOOP;

END
$$

DO $$
DECLARE
r record;
j jsonb;
prc_curs refcursor;

BEGIN

  prc_curs = "Функция, которая возвращает курсор"(параметры);

  LOOP
  FETCH prc_curs INTO r;
  exit WHEN NOT FOUND;
  --SELECT row_to_json(r)::jsonb j;
  --  RAISE info '%', row_to_json(r)::jsonb;--r;

  j = row_to_json(r)::jsonb;

  j = jsonb_set(j, '{i_doc_id}', '197404470001', false);

  j = jsonb_set(j, '{vc_op_status$}', '"I"', true);

  -- RAISE NOTICE '%', j;

  PERFORM "Функция, которая принимает JSONB"(j);


  END LOOP;

END
$$