在MongoDB中使用MapReduce的共同好友

Question

我正在MongoDB中尝试MapReduce，我有以下数据类型的MongoDB集合

{ "_id" : ObjectId("57aea85af405910cfcd2bfeb"), "friendList" : [ "Karma", " Tom", " Ram", " Bindu", " Shiva", " Kishna", " Bikash", " Bakshi", " Dinesh" ], "user" : "Hari" }

{ "_id" : ObjectId("57aea85bf405910cfcd2bfec"), "friendList" : [ "Karma", " Sita", " Bakshi", " Hanks", " Shyam", " Bikash" ], "user" : "Howard" }

{ "_id" : ObjectId("57aea85cf405910cfcd2bfed"), "friendList" : [ "Dinesh", " Ram", " Hanks", " Bindu", " Howard", " Bikash", " Shyam", " Bakshi" ], "user" : "Sita" }

{ "_id" : ObjectId("57aea85cf405910cfcd2bfee"), "friendList" : [ "Hanks", " Tom", " Karma", " Hari", " Dinesh" ], "user" : "Shiva" }

{ "_id" : ObjectId("57aea85cf405910cfcd2bfef"), "friendList" : [ "Bakshi", " Kishna", " Hanks", " Shiva", " Bindu", " Hari", " Karma", " Sita" ], "user" : "Dinesh" }

我的代码

^{2}$

在map函数中，我已经完成了排序，并且形成了复合键，以便相同的键通过相同的reducer，即reduce（）函数的输入

Map（）输出：

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

现在在reducer中，我想合并具有相同钥匙。但是我的reduce函数不起作用了吗？在

预期输出

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