2018年NodeJS Express Mongoose API的MongoDB非重复计数

const mongoose = require('mongoose');

// 连接MongoDB数据库
mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true });

// 定义Mongoose模型
const MyModel = mongoose.model('MyModel', new mongoose.Schema({
  field: String
}));

MyModel.aggregate([
  { $group: { _id: '$field', count: { $sum: 1 } } },
  { $group: { _id: null, distinctCount: { $sum: 1 } } }
])
.exec((err, result) => {
  if (err) {
    console.error(err);
  } else {
    console.log('非重复计数结果:', result[0].distinctCount);
  }
});

const express = require('express');
const app = express();

app.get('/api/nonDuplicateCount', (req, res) => {
  MyModel.aggregate([
    { $group: { _id: '$field', count: { $sum: 1 } } },
    { $group: { _id: null, distinctCount: { $sum: 1 } } }
  ])
  .exec((err, result) => {
    if (err) {
      console.error(err);
      res.status(500).json({ error: 'Internal server error' });
    } else {
      res.json({ distinctCount: result[0].distinctCount });
    }
  });
});

app.listen(3000, () => {
  console.log('API server listening on port 3000');
});