需要获取mongodb上复杂数据的平均值

{
  "_id": 1,
  "name": "Alice",
  "scores": [
    { "subject": "Math", "score": 85 },
    { "subject": "Science", "score": 90 }
  ]
},
{
  "_id": 2,
  "name": "Bob",
  "scores": [
    { "subject": "Math", "score": 78 },
    { "subject": "Science", "score": 88 }
  ]
}

db.students.aggregate([
  {
    $unwind: "$scores"
  },
  {
    $group: {
      _id: null,
      averageScore: { $avg: "$scores.score" }
    }
  }
])

db.students.aggregate([
  {
    $unwind: "$scores"
  },
  {
    $group: {
      _id: null,
      averageScore: { $avg: "$scores.score" }
    }
  }
])

db.students.aggregate([
  {
    $unwind: "$scores"
  },
  {
    $addFields: {
      "scores.score": { $toInt: "$scores.score" }
    }
  },
  {
    $group: {
      _id: null,
      averageScore: { $avg: "$scores.score" }
    }
  }
])

db.students.aggregate([
  {
    $unwind: "$scores"
  },
  {
    $group: {
      _id: null,
      averageScore: { $avg: "$scores.score" }
    }
  }
], { allowDiskUse: true })