MongoDB聚合，$addFields不在$cond上工作

我一直在使用调查收集和$lookup来查找调查问题的相关答案

现在我想引入一个user\u oid并使用$addField创建一个“user\u answer\u count”

代码：

Survey.aggregate([
    { $match: { team_oid: mongoose.Types.ObjectId(req.params.t_oid) } },
    { $addFields: { count_questions: { $size: "$questions"} } },
    { $unwind: { path: "$questions" } },


    { $lookup: { from: 'answers', localField: 'questions', foreignField: 'question_oid', as: 'answer' } },
    { $unwind: { path: "$answer", preserveNullAndEmptyArrays: true } },
    { $addFields: { 
        answer_count: { $cond: [{ $eq: [{ $type: "$answer" }, "object" ]}, 1, 0] } },
        user_answer_count: { $cond: [{ $eq: ["$answer.user_oid", mongoose.Types.ObjectId(req.params.u_oid) ]}, 1, 0] }
    },


    { $lookup: { from: 'votes', localField: '_id', foreignField: 'surveyOid', as: 'votes' } },
    { $unwind: { path: "$votes", preserveNullAndEmptyArrays: true } },
    { $addFields: { vote_count: { $cond: [{ $eq: [{ $type: "$votes" }, "object"] }, 0.2, 0] } } },

    {
      $group: {
        _id: "$_id",
        huddle_number: { $first: "$huddle_number" },
        count_questions: { $first: "$count_questions" },
        count_answers: { $sum: "$answer_count" },
        count_votes: { $sum: "$vote_count" },
        count_user_answers: { $sum: "$user_answer_count" },
        sefirot_state: { $first: "$sefirot_state" },
        created_date: { $first: "$created_date" },
        avg_positive: { $avg: "$answer.positive" },
        avg_creative: { $avg: "$answer.creative" },
        avg_focused: { $avg: "$answer.focused" },
        avg_friendly: { $avg: "$answer.friendly" },
        avg_aligned: { $avg: "$answer.aligned" },
        avg_alert: { $avg: "$answer.alert" }
      }
    }
]).exec((err, doc) => {

这里的一切都很有效，第一个$addField“answer\u count”非常有效。但是第二个“用户回答计数”却失败了

控制台显示：

参数必须是聚合管道运算符

这是我第一次尝试将$lookup与$addFields结合使用，因此，非常感谢您的建议

编辑：

Survey.aggregate([
    { $match: { team_oid: mongoose.Types.ObjectId(req.params.t_oid) } },
    { $addFields: { count_questions: { $size: "$questions"} } },
    { $unwind: { path: "$questions" } },


    { $lookup: { from: 'answers', localField: 'questions', foreignField: 'question_oid', as: 'answer' } },
    { $unwind: { path: "$answer", preserveNullAndEmptyArrays: true } },
    { $addFields: { 
        answer_count: { $cond: [{ $eq: [{ $type: "$answer" }, "object" ]}, 1, 0] } },
        user_answer_count: { $cond: [{ $eq: ["$answer.user_oid", mongoose.Types.ObjectId(req.params.u_oid) ]}, 1, 0] }
    },


    { $lookup: { from: 'votes', localField: '_id', foreignField: 'surveyOid', as: 'votes' } },
    { $unwind: { path: "$votes", preserveNullAndEmptyArrays: true } },
    { $addFields: { vote_count: { $cond: [{ $eq: [{ $type: "$votes" }, "object"] }, 0.2, 0] } } },

    {
      $group: {
        _id: "$_id",
        huddle_number: { $first: "$huddle_number" },
        count_questions: { $first: "$count_questions" },
        count_answers: { $sum: "$answer_count" },
        count_votes: { $sum: "$vote_count" },
        count_user_answers: { $sum: "$user_answer_count" },
        sefirot_state: { $first: "$sefirot_state" },
        created_date: { $first: "$created_date" },
        avg_positive: { $avg: "$answer.positive" },
        avg_creative: { $avg: "$answer.creative" },
        avg_focused: { $avg: "$answer.focused" },
        avg_friendly: { $avg: "$answer.friendly" },
        avg_aligned: { $avg: "$answer.aligned" },
        avg_alert: { $avg: "$answer.alert" }
      }
    }
]).exec((err, doc) => {

示例文档

**Survey**
_id : 5f5a372d9ea9981e7c5773cb
questions :
    0 : 5f522b025dd8993e58283522
    1 : 5f47a892db023557105e2be3
    2 : 5f522a9d5dd8993e58283520
    3 : 5f0e23ef2e0fcb3fe04a7314
    4 : 5f522b285dd8993e58283523
created_date : 2020-09-10T14:24:45.439+00:00
team_oid : 5f44cc20c74f8a444851d9c2
huddle_number : 22
sefirot_state : "Aligned"
__v : 0

**Answer**
_id : 5f58bb04772a5943a0b54ec9
question : "What does "winning" look like in this team?"
question_oid : 5f522bc55dd8993e58283526
user_team_oid : 5f44cc20c74f8a444851d9c2
user_oid : 5f1ef3e8accff82f3cae3957
comment : "It means Cobra Kai Never Die and Only Get Better"
created_date : 2020-09-09T11:22:44.098+00:00
__v : 0

---

有一些修复，缺少括号和

$cond

语法不正确，而且这种方法获取数组计数是错误的

• 计数数组中的元素数使用

  $size

  ，用于

  回答\u计数

• 您可以使用

  $reduce

  数组运算符按用户获取计数，无需使用

  $unwind

  应答数组

---

谢谢@turivishal-我试过了，但也犯了同样的错误…谢谢@turivishal。这是一个有用的答案，它工作得很好，但是当我应用到我的代码时，它不起作用。我想因为我在

aggregate

方法中执行之前的操作，所以数据已经结构化了？如果您想看一看，我在问题中添加了其余的聚合。我正在努力解决这个问题。再次感谢，如果我能完成这项工作，我会接受这个答案。好的，为操场上的其他收藏提供一些文件，所以我会调查它