MongoDB - TypeError: users.aggregate is not a function

Question

I'm trying to query a collection using aggregate but getting TypeError: users.aggregate is not a function. Here's my code:

./app.js (reduced to fit)

var express = require('express');
var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/mydb');
var users = require('./routes/users');
var app = express();

app.use(function(req, res, next) {
    req.db = db;
    next();
});

app.use('/users', users);
module.exports = app;

./routes/users.js

var express = require('express');
var router = express.Router();

router.get('/test', function(req, res) {
  var users = req.db.get('users');

  users.aggregate([{ $match: { username: 'test0' }}], function(err, data) {
    res.json(data);
  });
});

module.exports = router;

I'm running MongoDB version 3.2.10 and the above query works fine in the console. I've looked up solutions and they all suggest to check the MongoDB version, which I've already done. I've also tried req.db.collection('users').aggregate (as suggested by another post) and receive a similar error: req.db.collection is not a function. What am I missing?

EDIT: Running users.find({ username: 'test0' }, func... works and returns correct data.

EDIT2: Added more code.

Deeper searching found that monk is incompatible with aggregate and I must use users.col.aggregate(). Answered here: stackoverflow.com/questions/23951123/… — TestWell
– TestWell, Commented Nov 2, 2016 at 2:32

Hein Zeya · Accepted Answer · 2016-11-01 02:26:28Z

1

You can do like this.

var app = require('express')();
var expressMongoDb = require('express-mongo-db');

app.use(expressMongoDb('mongodb://localhost/test'));

app.get('/', function (req, res, next) {
  req.db // => Db object
});

answered Nov 1, 2016 at 2:26

Hein Zeya

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1 Comment

TestWell Over a year ago

I'm returning the database just fine in my req.db.get('users'). I'm able to find(), findOne(), update(), and insert() to it, but aggregate is failing.

Hein Zeya · Accepted Answer · 2016-11-01 04:46:11Z

0

I tried with this. It is working in my local.

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

const db = require('monk')('localhost/test')

app.use(function(req,res,next){
 req.db = db;
 next();
});

app.get('/', function (req, res, next) {
  var db = req.db;
  var users = db.get('users');

  users.aggregate([
   {$match: { firstName: 'Test 2' }}
    ]).then(function(docs) {
    console.log(docs)
    })
 });

 app.listen(3010, function () {
  console.log('Example app listening on port 3010!');
 });

answered Nov 1, 2016 at 4:46

Hein Zeya

112 bronze badges

1 Comment

TestWell Over a year ago

Thanks for your time, but I found an answer after specifically searching for monk library issues with aggregate. It turns out, it's not supported and I had to use the users collection with users.col.aggregate()

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