Question

我是mongodb的新手，对于应用程序，我有架构，

{
  date: "date",
  data:"encrypted data",
  sender:"sender",
  receiver:"receiver"
}

我希望在一个对象中有一组记录，其中发送者/接收者名称的组别不等于特定值。对于前。

{
  date: "date",
  data:"encrypted data",
  sender:"xyz",
  receiver:"abc"
},
{
  date: "date",
  data:"encrypted data",
  sender:"abc",
  receiver:"xyz"
},
{
  date: "date",
  data:"encrypted data",
  sender:"pqr",
  receiver:"abc"
},
{
  date: "date",
  data:"encrypted data",
  sender:"abc",
  receiver:"pqr"
},
{
  date: "date",
  data:"encrypted data",
  sender:"pqr",
  receiver:"xyz"
},
{
  date: "date",
  data:"encrypted data",
  sender:"xyz",
  receiver:"pqr"
}

当我使用find（abc）和一些组函数时，我需要采用以下格式的数据。

{
xyz:[
    {
      date: "date",
      data:"encrypted data",
      sender:"xyz",
      receiver:"abc"
    },
    {
      date: "date",
      data:"encrypted data",
      sender:"abc",
      receiver:"xyz"
    }
    ],
pqr:[
    {
      date: "date",
      data:"encrypted data",
      sender:"pqr",
      receiver:"abc"
    },
    {
      date: "date",
      data:"encrypted data",
      sender:"abc",
      receiver:"pqr"
    }
    ]
}

如何使用$ group或mongodb的任何其他功能，以给定格式提供结果？

Answer 1

使用 aggregation framework 来获得所需的结果。聚合管道只有初始$project阶段，它会重新整形流中的每个文档，例如只删除mongodb的_id字段，因为您在输出中不需要它。

下一个管道阶段是$group运算符步骤，它按指定的标识符receiver键对前一个$project阶段的输入文档进行分组，并应用累加器表达式$addToSet只需将系统变量$$ROOT添加到数组data的每个组。

获得聚合管道后，您需要使用其光标的forEach()方法迭代聚合结果以创建最终结果对象：

var result = {};
db.collection.aggregate([
    {
        "$project": {
            "_id": 0,
            "date": 1,
            "data": 1,
            "sender": 1,
            "receiver": 1
        }
    },
    {
        "$group": {
            "_id": "$receiver",
            "data": {
                "$addToSet": "$$ROOT"
            }
        }
    }
]).forEach(function (doc){
        result[doc._id] = doc.data
});
printjson(result);

<强>输出：

{
        "pqr" : [
                {
                        "date" : "date",
                        "data" : "encrypted data",
                        "sender" : "xyz",
                        "receiver" : "pqr"
                },
                {
                        "date" : "date",
                        "data" : "encrypted data",
                        "sender" : "abc",
                        "receiver" : "pqr"
                }
        ],
        "xyz" : [
                {
                        "date" : "date",
                        "data" : "encrypted data",
                        "sender" : "pqr",
                        "receiver" : "xyz"
                },
                {
                        "date" : "date",
                        "data" : "encrypted data",
                        "sender" : "abc",
                        "receiver" : "xyz"
                }
        ],
        "abc" : [
                {
                        "date" : "date",
                        "data" : "encrypted data",
                        "sender" : "pqr",
                        "receiver" : "abc"
                },
                {
                        "date" : "date",
                        "data" : "encrypted data",
                        "sender" : "xyz",
                        "receiver" : "abc"
                }
        ]
}

使用mongodb记录分组

1 个答案: