如何查询以实现得分最高的文档排名

Question

在 MongoDB 中文档以这种格式保存。 我想以这样一种方式提取数据，即 userId 具有最高 Rank 的最大总点数。我是 MongoDB 的新手。请帮助我如何使用查询。

此数据保存在 MongoDB 中。

  [{
    _id:"33fa7277-d882-4add-9985-e92c3e48c15b",
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06141",
    points_total:280
},
{
    _id:"33fa7277-d882-4add-9985-e92c3e48c25b",
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06142",
    points_total:200
},
{
    _id:"33fa7277-d882-4add-9985-e92c3e48c35b",
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06141",
    points_total:20
},
{
    _id:"33fa7277-d882-4add-9985-e92c3e48c45b",
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06144",
    points_total:150
}]

我试过这个查询，但没有用。

db.users.aggregate([
    { "$sort": {"points_total" : -1}},
    { "$group": {
      "_id": "$user_id",
      "points_total":{"$sum": "$points_total"},
      "items": { "$push": "$$ROOT" }
    }},
    { "$unwind": { "path": "$items", "includeArrayIndex": "items.rank" } },
    { "$replaceRoot": { "newRoot": "$items" } },
    { "$sort": { "points_total" : -1} }
  ])

预期输出

[{
   
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06141",
    points_total:300,
    rank:1
},
{
  
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06142",
    points_total:200,
    rank:2
},
{
   
    user_id:"a86302a0-2b5b-4392-95c6-6b41a4d06144",
    points_total:150,
    rank:3
}]

Answer 1

在申请$unwind之前，您还需要一个$group，以便将所有用户放在一个数组中：

db.users.aggregate([
    {
        $group: {
            _id: "$user_id",
            points_total: { $sum: "$points_total" }
        }
    },
    {
        $sort: { points_total: -1 }
    },
    {
        $group: {
            _id: null,
            users: { $push: { user_id: "$_id", points_total: "$points_total" } }
        }
    },
    { "$unwind": { "path": "$users", "includeArrayIndex": "users.rank" } },
    {
        $replaceRoot: {
            newRoot: "$users"
        }
    },
    {
        $addFields: {
            rank:  { $add: [ "$rank", 1 ] }
        }
    }
])

Mongo Playground