如何使用mongoose聚合来根据字段获取两个匹配文档的总和

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => {
    console.log('Connected to MongoDB');
  })
  .catch((error) => {
    console.error('Error connecting to MongoDB', error);
  });

const documentSchema = new mongoose.Schema({
  field1: String,
  field2: Number
});

const Document = mongoose.model('Document', documentSchema);

Document.aggregate([
  {
    $match: {
      field1: 'value1' // 根据字段1进行匹配
    }
  },
  {
    $group: {
      _id: null,
      total: { $sum: '$field2' } // 对字段2进行求和
    }
  }
])
  .then((result) => {
    console.log('Total sum:', result[0].total);
  })
  .catch((error) => {
    console.error('Error aggregating documents', error);
  });