MongoDB在对象数组中获取嵌套在对象数组中的单个对象

Question

如何根据一些属性值访问嵌套在对象数组中的单个对象，该对象数组嵌套在另一个对象数组中，类似于伪代码中的内容：

选择 DAY=1 WHERE _id=5a3469f22dc3784bdd9a6190 AND MONTH=12

Mongoose 模型架构如下所示。根据需要，子文档的列表高于其对应的父文档，dailySchedulesSchema 最高：

var dailySchedulesSchema = new mongoose.Schema({
    day: Number,
    dayStart: Number,
    firstBreakStart: Number,
    firstBreakEnd: Number,
    lunchStart: Number,
    lunchEnd: Number,
    secondBreakStart: Number,
    secondBreakEnd: Number,
    dayEnd: Number,
    workDuration: Number
});

var monthlyScheduleSchema = new mongoose.Schema({
    month: {type: Number, required: true },
    dailySchedules: [dailySchedulesSchema]
});

var employeeSchema = new mongoose.Schema({
    name: {type: String, required: true},
    surname: {type: String, required: true},
    email: {type: String, required: true},
    phone: {type: String, required: true},
    occupation: {type: String, required: true},
    status: {type: Boolean, required: true},
    monthlySchedule: [monthlyScheduleSchema]
});

这是我正在尝试处理的数据库中的员工条目。：

"_id" : ObjectId("5a3469f22dc3784bdd9a6190"),
        "name" : "Eric",
        "surname" : "K. Farrell",
        "email" : "EricKFarrell@dayrep.com",
        "phone" : "864-506-7281",
        "occupation" : "Employee",
        "status" : true,
        "monthlySchedule" : [
                {
                        "month" : 12,
                        "dailySchedules" : [
                                {
                                        "day" : 1,
                                        "dayStart" : 480,
                                        "firstBreakStart" : 600,
                                        "firstBreakEnd" : 615,
                                        "lunchStart" : 720,
                                        "lunchEnd" : 750,
                                        "secondBreakStart" : 870,
                                        "secondBreakEnd" : 885,
                                        "dayEnd" : 1020,
                                        "workDuration" : 480
                                },
                                {
                                        "day" : 2,
                                        "dayStart" : 540,
                                        "firstBreakStart" : 630,
                                        "firstBreakEnd" : 645,
                                        "lunchStart" : 750,
                                        "lunchEnd" : 780,
                                        "secondBreakStart" : 870,
                                        "secondBreakEnd" : 885,
                                        "dayEnd" : 1050,
                                        "workDuration" : 480
                                }
                        ]
                }
        ]
}

获取单日的路线本身是："/employees/:employeeid/:month/:day"。

虽然我设法访问了父文档（例如列出所有员工），但我无法列出特定的子文档条目（例如该员工的具体日程安排） - mongoose 要么已返回当月的所有现有日程安排或者什么都没有：

(...)

  var sendJsonResponse = function(res, status, content){
        res.status(status);
        res.json(content);
    }

(...)

module.exports.empDayReadOne = function(req, res){
    var monthParam = req.params.month;
    var employeeid = req.params.employeeid;
    var dayParam = req.params.day;

    Emp
        .aggregate([
        {$match: {$and: [{'monthlySchedule': {$elemMatch: {$exists: true} } }, {_id: employeeid }] } },
        {$unwind:'$monthlySchedule'}, 
        {$unwind:'$monthlySchedule.dailySchedules'}, 
        {$match:{ $and:[ {'monthlySchedule.dailySchedules.day': dayParam},{'monthlySchedule.month': monthParam} ] } }

        ])
        .exec(function(err, dailySchedule){
            if(dailySchedule){
                sendJsonResponse(res, 200, dailySchedule);
            } else if(err){
                sendJsonResponse(res, 400, err);
                return;
            } else {
                sendJsonResponse(res, 404, {"message": "This day has no schedules added."});
                return;
            }

        });

};

Answer 1

您可以尝试以下聚合查询。

下面的查询首先是$filtersmonthlySchedule，它返回具有匹配月份数组元素的数组，然后是第二个过滤器以检索dailySchedules数组中匹配的日期元素。

$arrayElemAt 将具有单个元素的数组转换为文档。

db.collection_name.aggregate([
  {"$match":{"_id":ObjectId("5a3469f22dc3784bdd9a6190")}},
  {"$project":{
    "dailyschedule":{
      "$arrayElemAt":[
        {"$filter":{
          "input":{
            "$filter":{
              "input":"$monthlySchedule",
              "cond":{"$eq":["$$this.month",12]}
            }
          },
          "cond":{"$eq":["$$this.day",1]
          }
        }},
      0]
    }
  }}
])

更新了 Mongoose 代码：

Emp.aggregate([
  {"$match":{"_id":mongoose.Types.ObjectId(employeeid)}},
  {"$project":{
    "dailyschedule":{
      "$arrayElemAt":[
        {"$filter":{
          "input":{
            "$filter":{
              "input":"$monthlySchedule",
              "cond":{"$eq":["$$this.month",monthParam]}
            }
          },
          "cond":{"$eq":["$$this.day",dayParam]
          }
        }},
      0]
    }
  }}
])