在 MongoDB 中执行排序查询

Question

我想在 MongoDB 中进行这个复杂的排序查询，但我未能实现。

集合中的模型如下所示：

_id: UUID('some-id'),
isDeleted: false,
date: ISODate('some-date'),
responses: [{
    _id: UUID('some-id'),
    userId: UUID('some-id'),
    response: 0
}, {
    _id: UUID('some-id'),
    userId: UUID('some-id'),
    response: 1
}]

要记住的一件事是，响应数组中始终包含 2 或 3 个对象。不多也不少。此外，响应将只有三个值，0、1 或 2。

我想做的是根据每个用户的反应对它们进行不同的排序。

所以假设我的名为 Events 的集合在数据库中有很多对象。我希望当我过滤它们时，排序将像这样完成：

If my response is 0 and others are either 0 or 1, then sort them always first.

If all responses are 1, sort them after.

Others (if any response is 2, or if my response is 1 but others are 1 or 0), sort them last.

我们可以通过在查询中传递 userId 来确定是否是我的回复。

最重要的是，我需要分页，所以我需要实现 $skip 和 $limit。

尝试使用 $unwind 然后 $project 尝试做一些基于 scoring 的排序，但无法实现。

得分排序看起来像这样：

if my response is 0 and others are 0 or 1 -> score = 100

if all responses are 1 -> score = 50

all others -> score = 0

这样我们就可以按分数排序了。但我不知道如何实际创建这个属性。

我想我们可以像这样创建一个属性：

$project: {
    myScore: {
        $cond: {
            if: {
                $in: [
                    UUID('my-user-id'),
                    "$responses.userId"
                ],
                then: "$respones.response", //this is returning array here with all responses
                else: 0
            }
        }
    },
    totalScore: {
        $sum: "$respones.response"
    }
}

然后我们可以进行另一个阶段，以某种方式对这些数字进行排序。

谢谢！ :)

Answer 1

这里是一个稍微简化的输入集。我们还包含一个 target 字段以帮助测试评分算法；对于最终的流水线，它不是必需的，其中 score 是 A、B、C，表示排序顺序中的第一个、中间的和最后一个。只要排序正确，分数可以是“任何东西”。我使用了 A、B 和 C，因为它在视觉上与我们正在查看的响应代码 (0,1,2) 不同，因此管道函数更容易理解，但它可能是 10、20、30 或 5,10 ,15.

var myUserId = 1;

var r = [
    {
        target: 'C', // last, myUserId response is 1                              
        responses: [
            {userId:0, response:0},
            {userId:1, response:1}
        ]
    }
    ,{
        target: 'C', // last, myUserId response is 1                              
        responses: [
            {userId:1, response:1},
            {userId:0, response:0}
        ]
    }
    ,{
        target: 'A', // first, myUserId response is 0                             
        responses: [
            {userId:1, response:0},
            {userId:0, response:0}
        ]
    }
    ,{
        target: 'B', // mid, all 1s                                               
        responses: [
            {userId:7, response:1},
            {userId:9, response:1}
        ]
    }
    ,{
        target: 'C',  // last, a 2 exists                                         
        responses: [
            {userId:4, response:2},
            {userId:3, response:1},
            {userId:1, response:0}
        ]
    }
];

此管道将产生所需的输出：

db.foo.aggregate([
    {$addFields: {score:
          {$cond: [
              {$in: [2, '$responses.response']}, // any 2s?                       
              'C', // yes, assign last                                            

              {$cond: [ // else                                                   
                  // All responses 1 (i.e. set diff is from 1 is empty set []?    
                  {$eq: [ {$setDifference:['$responses.response',[1]]}, [] ] },
                  'B', // yes, assign mid                                         

                  {$cond: [ // else                                               
                      // Does myUserId have a response of 0?  filter the 
                      // array on these 2 fields and if the size of the 
                      // filtered array != 0, that means you found one!                     
                      {$ne:[0, {$size:{$filter:{input:'$responses',
                                cond:{$and:[
                                    {$eq:['$$this.userId',myUserId]},
                                    {$eq:['$$this.response',0]}
                                ]}
                           }} } ]},
                      'A', // yes, assign first                                   
                      'C',  // else last for rest                                 
                  ]}
          ]}
          ]}
    }}

    ,{$sort: {'score':1}}

    // TEST: Show items where target DOES NOT equal score.  If the pipeline
    // logic is working, this stage will produce zero output; that's
    // how you know it works.                       
    //,{$match: {$expr: {$ne:['$score','$target']}} }
]);

Answer 2

任何想知道这个的人，这就是我想出的。 p.s。我还决定，如果任何响应包含响应 2，我需要忽略所有项目，因此我将只关注值 0 和 1。

db.invites.aggregate([
    {
        $match: {
            "$responses.response": {
                $ne: 2
            }
        }
    },
    {
        $addFields: {
            "myScore": {
              "$let": {
                "vars": {
                       "invite": {
                          // get only object that contains my userId and get firs item from the list (as it will always be one in the list)
                          "$arrayElemAt": [{
                            "$filter": {
                                  "input": "$responses",
                                  "as": "item",
                                  "cond": {"$eq": ["$$item.userId", UUID('some-id')]}
                          }} ,0]
                        }   
                  },
                  // ger response value of that object that contains my userId
                  "in": "$$invite.response"
              }
            },
            // as they are only 0 and 1s in the array items, we can see how many percent have voted with one.
            // totalScore = sum(responses.response) / size(responses)
            "totalScore": {
              $divide: [{$sum: "$responses.response"} , {$size: "$responses"}]
            }
        }
    },
    {
        $sort: {
            //sort by my score, so if I have responded with 0, show first
            "myScore": 1,
            //sort by totalScore, so if I have responded 1, show those that have all 1s first.
            "totalScore": -1
        }
    }
])

在 MongoDB 中执行排序查询

Performing sorting query in MongoDB

mongodb

mongodb-query

aggregation-framework