使用mongoDB从不同的值中提取两个字段

Question

以下是我的数据库的结构：

 { 
 "_id" : "aaaaaaaaaaaaaaaaaaaaaaaa",
 "risks" : [ 
    {
        "attrib" : "totalWeight", 
           "attribName" :"poids",
        "conditions" : [ 
            {
                "value" : 0,
                "operator" : "!==",
                "min" : "totalWeight",
                "strictComparator" : false,
                "message" : "PTC ou charge utile incorrects !"
            }
        ]
    }, 
  }

我希望获得一个包含不同attrib且值为attribName的列表：

{"attrib": "totalWeight", "attribName":"poids"}

这个查询给我一个由空对象组成的结果::

aggregate([{"$group": {"_id": "$risks.attrib"}},{"$project":{"_id":0,"id1":"$risks.attrib","text": "$risks.attribName"}}])