javascript - 错误 : Collection method aggregate is synchronous

Question

我正在尝试以下代码:

const Conn = mongoose.createConnection('mongodb://127.0.0.1:27017/db');

const addresses = Conn.collection('users').aggregate([
  {
    $project: {
      _id: false,
      ethAddr: true,
    }
  }
]);

我收到以下错误:

[...]\backend\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:100
        throw new Error('Collection method ' + i + ' is synchronous');
              ^

Error: Collection method aggregate is synchronous
    at NativeCollection.<computed> [as aggregate] ([...]\backend\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:100:15)
    at file:///[...]/backend/scripts/dbGetMerkleRoot.js:11:46
    at file:///[...]/backend/scripts/dbGetMerkleRoot.js:28:3
    at ModuleJob.run (node:internal/modules/esm/module_job:185:25)
    at async Promise.all (index 0)
    at async ESMLoader.import (node:internal/modules/esm/loader:281:24)
    at async loadESM (node:internal/process/esm_loader:88:5)
    at async handleMainPromise (node:internal/modules/run_main:65:12)

我做错了什么？

Answer 1

好像是mongoose连接数据库的方式有问题。在调用聚合方法之前创建连接但不连接会导致抛出该异常。我应该这样使用它:

// create custom connection
const Conn = mongoose.createConnection();

// connect to database
await Conn.openUri('mongodb://127.0.0.1:27017/db');

// @type {AggregationCursor}
const addresses = Conn.collection('users').aggregate([
  {
    $project: {
      _id: false,
      ethAddr: true,
    }
  }
]);

console.log( await addresses.toArray() );

令人沮丧的是，异常本身的记录很差。