Postgres || for json instead of jsonb

json_merge_objects.sql

CREATE OR REPLACE FUNCTION json_merge_objects(a json, b json) RETURNS json
LANGUAGE SQL IMMUTABLE AS $$
WITH combined AS (
  SELECT pair.key, pair.value FROM json_each(a) AS pair
  UNION ALL
  SELECT pair.key, pair.value FROM json_each(b) AS pair
)
SELECT json_object_agg(key, value) 
FROM combined
$$;