java - Mongodb 获取唯一值的计数

Question

我有这样的数据收集

{
    "_id" : ObjectId("58a42914eef0ba24b49cbf3a"),
    "user" : "111",
    "contact" : "555"
},
{
    "_id" : ObjectId("58a42922eef0ba24b49cbf3b"),
    "user" : "111",
    "contact" : "666"
},
{
    "_id" : ObjectId("58a4292deef0ba24b49cbf3c"),
    "user" : "111",
    "contact" : "666"
},
{
    "_id" : ObjectId("58a42934eef0ba24b49cbf3d"),
    "user" : "222",
    "contact" : "666"
},
{
    "_id" : ObjectId("58a42938eef0ba24b49cbf3e"),
    "user" : "222",
    "contact" : "777"
},
{
    "_id" : ObjectId("58a4293eeef0ba24b49cbf3f"),
    "user" : "222",
    "contact" : "888"
},
{
    "_id" : ObjectId("58a4293feef0ba24b49cbf40"),
    "user" : "222",
    "contact" : "888"
},
{
    "_id" : ObjectId("58a42941eef0ba24b49cbf41"),
    "user" : "222",
    "contact" : "888"
},
{
    "_id" : ObjectId("58a42947eef0ba24b49cbf42"),
    "user" : "333",
    "contact" : "888"
},
{
    "_id" : ObjectId("58a4294ceef0ba24b49cbf43"),
    "user" : "333",
    "contact" : "666"
},

我能否获得列出每个用户中的联系人及其计数的结果，就像 Java 中的这样？

{user:user_name,data[contact:count]}

所以结果应该如下所示，每个用户都有一个联系人列表及其计数

{user:111,contact:[{555:1},{666:2}]},{user:222,contact:[{666:1},{777:1},{888:3}]},{user:333,contact:[{888:1},{666:1}]} 

提前致谢

Answer 1

所以这个想法是$group几次，首先在对user和contact进行分组时计算计数，并对进行其他分组>user 推送联系人 和计数。我已经包含了需要更改的查询区域

db.data.aggregate([{
    $group: {
        _id: {
            user: "$user",
            contact: "$contact"
        },
        count: {
            $sum: 1
        }
    }
}, {
    $group: {
        _id: "$_id.user",
        uniqueIds: {
            $push: {
                contact: "$_id.contact",
                count: "$count"
            }
        }
    }
}])

您无法按照您想要的方式获得响应。您将始终拥有键和值对。

响应示例:

{
    "_id": "111",
    "uniqueIds": [{
        "contact": "555",
        "count": 1
    }, {
        "contact": "666",
        "count": 2
    }]
}