我正在使用MongoDB数据库，该数据库的收集模型包括 班级 ， 学生 ， 学科 和[学术] 表现 。以下是基于猫鼬的架构和模型：

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.Types.ObjectId;

// SUBJECT collection
var subjectSchema = new Schema({
    name        : { type: String, required: true },
    category    : { type: String, required: true }
});
var Subject = mongoose.model('Subject', subjectSchema);

// STUDENT collection
var studentSchema = new Schema({
    name        : { type: String, required: true },
    grade       : { type: Number, required: true }
});
var Student = mongoose.model('Student', studentSchema);

// PERFORMANCE collection
var performanceSchema = new Schema({
    subjectId   : { type: ObjectId, ref: Subject.modelName, required: true },
    score       : { type: Number, required: true },
    maximum     : { type: Number, required: true },
    grade       : { type: String, required: true }
});
var Performance = mongoose.model('Performance', performanceSchema);

// *Note*: This is just to use as a sub-document schema, and not as a collection
var classStudentSchema = new Schema({
    studentId   : { type: ObjectId, ref: Student.modelName, required: true },
    performance : [performanceSchema]
}, { _id: false });

// CLASS collection
var classSchema = new Schema({
    name        : { type: String, required: true },
    scores      : [classStudentSchema]
});
var Class = mongoose.model('Class', classSchema);

该class集合的文件是最复杂的地段; 示例文档为：

{
  "_id" : ObjectId("57758f15f68da08c254ebee1"),
  "name" : "Grade 5 - Section A",
  "scores" : [{
    "studentId" : ObjectId("5776bd36ffc8227405d364d2"),
    "performance": [{
      "subjectId" : ObjectId("577694ecbf6f3a781759c54a"),
      "score" : 86,
      "maximum" : 100,
      "grade" : "B+"
    }, {
      "subjectId" : ObjectId("5776ffe1804540e29c602a62"),
      "score" : 74,
      "maximum" : 100,
      "grade" : "A-"
    }]
  }, {
    "studentId" : ObjectId("5776bd36ffc8227405d364d5"),
    "performance": [{
      "subjectId" : ObjectId("577694ecbf6f3a781759c54a"),
      "score" : 94,
      "maximum" : 100,
      "grade" : "A"
    }, {
      "subjectId" : ObjectId("5776ffe1804540e29c602a62"),
      "score" : 81,
      "maximum" : 100,
      "grade" : "A"
    }]
  }]
}

我能够使用以下代码检索现有的班级文档并将其添加到分数中：

Class.findOne({ name: 'Grade 5 - Section A' }, function(err, class) {
  if (err) throw err;
  Student.findOne({ name: 'John Doe' }, function(err, student) {
    if (err) throw err;
    class.scores.push({
      studentId: student.id
    });
  };
});

但是，如何添加/更新/删除该特定学生的成绩？我需要能够class通过以下方式与集合进行交互：

• 检索所有学生或特定学生的分数（检索scores数组中的特定元素）
• 为特定主题添加/更新/删除特定学生的分数（在更新或删除的情况下，检索scores[n].performance数组中的特定元素；对于添加或添加到同一数组中。