如何对同一集合中不同文档的值求和? [英] How can I sum values from different documents in the same collection?

问题描述

I have photos with an array of likes. I am using mongoose as a db. I want to sum all the numeric values in the likes count of photo collection.
    exports.getAnalytics = (req, res) => {
  if (!req.user) {
    return res.redirect('/login');
  }
  Campaign.findOne({slug:req.params.slug}, (err, campaign) => {
    PhotoEntries.find({ CampaignId: campaign._id}, ['Photo','Name', 'done' ,'likes_count', ], {sort:{ _id: -1} }, function(err, photos) {
      
      PhotoEntries.countDocuments({CampaignId: campaign._id} , function (err, count) { 
          PhotoEntries.aggregate([
            {
              $group: {
                _id: "$CampaignId",
                Totallikes: { $sum: "$likes_count" }
              }
            }
          ]) 
    if(req.user){
      console.log(photos);
      res.render('admin/analytics', {
        title: 'Analytics',
        campaign: campaign,
        photolist : photos, 
        Count:count ,
        Totallikes: Totallikes  
        });
    }
  // }
  // ])

  });
  });
  });
  }   

但是它不起作用.错误是参数必须是聚合管道运算符.如何实现此目标?
这是我的架构代码.var photoSchema = new Schema({名称:{type:String}，电子邮件:{类型:字符串}，照片:{类型:字符串}，说明:{type:String}，电话号码:{type:String}，CampaignId:{类型:Schema.Types.ObjectId，ref:广告系列"，}

However it is not working. The error is Arguments must be aggregate pipeline operators. How can I achieve this?
Here is my schema code. var photoSchema = new Schema({ Name: {type: String}, Email: { type: String }, Photo: { type: String }, Description:{type:String}, PhoneNumber:{type:String}, CampaignId: { type: Schema.Types.ObjectId, ref: 'Campaigns', },

        done: {
          type: Boolean  ,
      },
    
      likes_count: Number ,default: 0,
        likedBy: [
          {
              type:Schema.Types.ObjectId,
              ref: "User"
          }
      ], 
      });
      }

我需要将 likes_count 字段添加到集合中的所有文档中.

I need to add the likes_count field to all documents in the collection.

推荐答案

您错过了输入 _id ，按指定的 _id 表达式对输入文档进行分组，并针对每个不同的分组输出文档.每个输出文档的 _id 字段均包含唯一的按值分组.有关更多信息，请参见 $ group

You missed input _id, Groups input documents by the specified _id expression and for each distinct grouping, outputs a document. The _id field of each output document contains the unique group by value. For more information refer $group

PhotoEntries.aggregate([
  {
    $group: {
      _id: null,
      Totallikes: { $sum: "$likes_count" }
    }
  }
])

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