PostgreSQL 比较两个 jsonb 对象

With PostgreSQL(v9.5) http://www.postgresql.org/, the JSONB https://stackoverflow.com/questions/22654170/explanation-of-jsonb-introduced-by-postgresql格式提供了绝佳的机会。但现在我陷入了看似相对简单的操作；

比较两个 jsonb 对象；查看一份文档与另一份文档相比有何不同或缺失。

到目前为止我所拥有的

WITH reports(id,DATA) AS (
          VALUES (1,'{"a":"aaa", "b":"bbb", "c":"ccc"}'::jsonb),
                 (2,'{"a":"aaa", "b":"jjj", "d":"ddd"}'::jsonb) )
SELECT jsonb_object_agg(anon_1.key, anon_1.value)
FROM
  (SELECT anon_2.key AS KEY,
      reports.data -> anon_2.KEY AS value
   FROM reports,
     (SELECT DISTINCT jsonb_object_keys(reports.data) AS KEY
      FROM reports) AS anon_2
   ORDER BY reports.id DESC) AS anon_1

应返回第 1 行与第 2 行相比的差异：

'{"b":"bbb", "c":"ccc", "d":null}'

相反，它也返回重复项（{"a": "aaa"}）。还;一般来说可能有更优雅的方法！

UPDATED

CREATE OR REPLACE FUNCTION jsonb_diff_val(val1 JSONB,val2 JSONB)
RETURNS JSONB AS $$
DECLARE
  result JSONB;
  v RECORD;
BEGIN
   result = val1;
   FOR v IN SELECT * FROM jsonb_each(val2) LOOP
     IF result @> jsonb_build_object(v.key,v.value)
        THEN result = result - v.key;
     ELSIF result ? v.key THEN CONTINUE;
     ELSE
        result = result || jsonb_build_object(v.key,'null');
     END IF;
   END LOOP;
   RETURN result;
END;
$$ LANGUAGE plpgsql;

Query:

SELECT jsonb_diff_val(
    '{"a":"aaa", "b":"bbb", "c":"ccc"}'::jsonb,
    '{"a":"aaa", "b":"jjj", "d":"ddd"}'::jsonb
);
            jsonb_diff_val             
---------------------------------------
 {"b": "bbb", "c": "ccc", "d": "null"}
(1 row)