javascript - 在 MapReduce MongoDB 中按键对数据进行分组

Question

我正在尝试 MongoDB 中的 MapReduce 程序来寻找共同的 friend ，我在对 mongoDB 中的键进行排序后获得了以下数据

{"user" : " Hari","friend" : "Shiva",
 "friendList": ["Hanks"," Tom"," Karma"," Hari"," Dinesh"]}


 {"user" : "Hari","friend" : " Shiva",
  "friendList" : ["Karma"," Tom"," Ram"," Bindu"," Shiva",
                   " Kishna"," Bikash"," Bakshi"," Dinesh"]}

现在我想将这些具有相同键的数据集分组到一个组中，在将键值对发送到 reducer 之前在 map 函数中使用 Javascript，我如何对数据进行分组？例如我想要这样的输出

{"user" : " Hari","friend" : "Shiva",
 "friendList": ["Hanks"," Tom"," Karma"," Hari"," Dinesh"],["Karma"," Tom"," Ram"," Bindu"," Shiva"," Kishna"," Bikash"," Bakshi"," Dinesh"]}

Answer 1

您可以将两条记录的 friendlist 数组连接成一个数组，以创建如下对象:

   {
  "_id": {
    "user": " Hari",
    "friend": "Shiva"
  },
  "value": {
    "friendList": [
      "Hanks",
      " Tom",
      " Karma",
      " Hari",
      " Dinesh",
      "Karma",
      " Tom",
      " Ram",
      " Bindu",
      " Shiva",
      " Kishna",
      " Bikash",
      " Bakshi",
      " Dinesh"
    ]
  }
}

请参阅 https://jsfiddle.net/b6hxswvk/1/ 处的代码创建这个单个对象

如果您希望好友列表 是一个二维数组，即像这样:

{
  "_id": {
    "user": " Hari",
    "friend": "Shiva"
  },
  "value": {
    "friendList": [
      [
        "Hanks",
        " Tom",
        " Karma",
        " Hari",
        " Dinesh"
      ],
      [
        "Karma",
        " Tom",
        " Ram",
        " Bindu",
        " Shiva",
        " Kishna",
        " Bikash",
        " Bakshi",
        " Dinesh"
      ]
    ]
  }
}

您可以使用 https://jsfiddle.net/b6hxswvk/2/ 处的代码