21

使用PostgreSQL(v9.5)，JSONB格式提供了绝佳的机会。但是现在我被一个看起来相对简单的操作所困扰。

比较两个 jsonb 对象；查看一份文件与另一份文件相比有何不同或缺失的地方。

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

应该返回第 1 行与第 2 行的差异：

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

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

4

4 回答 4

30

更新

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;

询问：

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)
于 2016-03-16T17:50:58.580 回答
15

我创建了类似的函数，它将递归地扫描对象并返回新对象和旧对象之间的差异。我无法找到一种“更好”的方法来确定 jsonb 对象是否“为空” - 所以如果有任何建议如何简化它，我将不胜感激。我计划使用它来跟踪对 jsonb 对象所做的更新，因此我只存储已更改的内容。

这是功能：

CREATE OR REPLACE FUNCTION jsonb_diff_val(val1 JSONB,val2 JSONB)
RETURNS JSONB AS $$
DECLARE
    result JSONB;
    object_result JSONB;
    i int;
    v RECORD;
BEGIN
    IF jsonb_typeof(val1) = 'null'
    THEN 
        RETURN val2;
    END IF;

    result = val1;
    FOR v IN SELECT * FROM jsonb_each(val1) LOOP
        result = result || jsonb_build_object(v.key, null);
    END LOOP;

    FOR v IN SELECT * FROM jsonb_each(val2) LOOP
        IF jsonb_typeof(val1->v.key) = 'object' AND jsonb_typeof(val2->v.key) = 'object'
        THEN
            object_result = jsonb_diff_val(val1->v.key, val2->v.key);
            -- check if result is not empty 
            i := (SELECT count(*) FROM jsonb_each(object_result));
            IF i = 0
            THEN 
                result = result - v.key; --if empty remove
            ELSE 
                result = result || jsonb_build_object(v.key,object_result);
            END IF;
        ELSIF val1->v.key = val2->v.key THEN 
            result = result - v.key;
        ELSE
            result = result || jsonb_build_object(v.key,v.value);
        END IF;
    END LOOP;

    RETURN result;

END;
$$ LANGUAGE plpgsql;

然后简单的查询如下所示：

SELECT jsonb_diff_val(                                                                                                                                                                                                                                                           
    '{"a":"aaa", "b":{"b1":"b","b2":"bb","b3":{"b3a":"aaa","b3c":"ccc"}}, "c":"ccc"}'::jsonb,
    '{"a":"aaa", "b":{"b1":"b1","b3":{"b3a":"aaa","b3c":"cccc"}}, "d":"ddd"}'::jsonb
);
                                jsonb_diff_val                                 
-------------------------------------------------------------------------------
 {"b": {"b1": "b1", "b2": null, "b3": {"b3c": "cccc"}}, "c": null, "d": "ddd"}
(1 row)
于 2016-05-17T13:54:30.777 回答
7

这是一个没有创建新功能的解决方案；

SELECT
    json_object_agg(COALESCE(old.key, new.key), old.value)
  FROM json_each_text('{"a":"aaa", "b":"bbb", "c":"ccc"}') old
  FULL OUTER JOIN json_each_text('{"a":"aaa", "b":"jjj", "d":"ddd"}') new ON new.key = old.key 
WHERE 
  new.value IS DISTINCT FROM old.value

结果是；

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

此方法仅比较第一级 json。它不会遍历整个对象树。

于 2019-04-25T14:46:00.660 回答
2

我的解决方案不是递归的，但您可以使用它来检测常见的键/值：

-- Diff two jsonb objects
CREATE TYPE jsonb_object_diff_result AS (
  old jsonb,
  new jsonb,
  same jsonb
);
CREATE OR REPLACE FUNCTION jsonb_object_diff(in_old jsonb, in_new jsonb)
RETURNS jsonb_object_diff_result AS
$jsonb_object_diff$
DECLARE
  _key text;
  _value jsonb;
  _old jsonb;
  _new jsonb;
  _same jsonb;
BEGIN
  _old := in_old;
  _new := in_new;

  FOR _key, _value IN SELECT * FROM jsonb_each(_old) LOOP
    IF (_new -> _key) = _value THEN
      _old := _old - _key;
      _new := _new - _key;
      IF _same IS NULL THEN
        _same := jsonb_build_object(_key, _value);
      ELSE
        _same := _same || jsonb_build_object(_key, _value);
      END IF;
    END IF;
  END LOOP;

  RETURN (_old, _new, _same);
END;
$jsonb_object_diff$
LANGUAGE plpgsql;

结果可能如下所示：

SELECT * FROM jsonb_object_diff(
  '{"a": 1, "b": 5, "extra1": "woo", "old_null": null, "just_null": null}'::jsonb,
  '{"a": 1, "b": 4, "extra2": "ahoj", "new_null": null, "just_null": null}'::jsonb);

-[ RECORD 1 ]--------------------------------------
old  | {"b": 5, "extra1": "woo", "old_null": null}
new  | {"b": 4, "extra2": "ahoj", "new_null": null}
same | {"a": 1, "just_null": null}
于 2017-09-16T11:31:59.280 回答