MongoDb查詢嵌套對象的數組字段

Question

我正在嘗試查詢喜歡該事件的所有用戶。 事件ID存儲在用戶文檔的嵌套對象中。

我的架構看起來像這樣

{
    email: {
      type: String,
      unique: true,
      required: [true, 'Email is required!'],
      trim: true,
      validate: {
        validator(email) {
          const emailRegex = /^[-a-z0-9%S_+]+(\.[-a-z0-9%S_+]+)*@(?:[a-z0-9-]{1,63}\.){1,125}[a-z]{2,63}$/i;
          return emailRegex.test(email);
        },
        message: '{VALUE} is not a valid email!',
      },
    },
    role: {
      type: String,
      enum: ['admin', 'user', 'planner'],
      default: 'user',
    },
    name: {
      type: String,
      trim: true,
    },
    username: {
      type: String,
      trim: true,
      unique: true,
    },
    password: {
      type: String,
      required: [true, 'Password is required!'],
      trim: true,
      minlength: [6, 'Password needs to be longer!'],
      validate: {
        validator(password) {
          return password.length >= 6 && password.match(/\d+/g);
        },
      },
    },
    picture: {type: String},
    favorites: {
      events: [
        {
          type: Schema.Types.ObjectId,
          ref: 'Event',
        },
      ],
    },
  }

我將如何編寫此查詢？

我已經嘗試過$elemMatch和普通查詢的各種組合

Answer 1

$elemMatch應該用作對象，但在數組favorites.events每個元素都是String（ObjectID），因此，應使用$eq將每個元素與String匹配，String是所需事件的ID。

解決方案是：

User.find({
    'favorites.events': {
        '$elemMatch': {
            '$eq': id
        }
    }
})

$elemMatch文檔在這里https://docs.mongodb.com/manual/reference/operator/query/elemMatch/#element-match

和$eq文檔在這里https://docs.mongodb.com/manual/reference/operator/query/eq/

您應該對Mongo的簡單結構提出疑問。 例如，這是我為您測試的問題

const Schema = mongoose.Schema;

const EventSchema = new Schema({
    title: String
})

const UserSchema = new Schema({
    username: String,
    favorites: {
        events: [{
            type: Schema.Types.ObjectId,
            ref: 'Event',
        }]
    }
});

const User = mongoose.model('User', UserSchema);
const Event = mongoose.model('Event', EventSchema)

app.get('/users/event/:id', (req, res) => {
    const {id} = req.params;
    console.log(id);
    User.find({
        'favorites.events': {
            '$elemMatch': {
                '$eq': id
            }
        }
    }).then(u => res.send(u)) })