Async: Combining two mongodb collection using Async.forEach

Question

I am very new to MEAN stack and i am trying to learn async.

I'm trying to combine two collections from the mongodb using async

and applied this iterate over a collection, perform an async task for each item, i'm a trying to learn the simplest and efficient way of doing this simple tasks so it will be easy to understand.

var OrderSchema = new mongoose.Schema({

    menu_id: {type:mongoose.Schema.Types.ObjectId, ref: 'Foods'},
    menu_name: {type:String,required:false},
    customer_id: {type:String,required: true,},
    customer_name:{type:String, required: false},
    table_no:{type:String,required:true},
    cooking:{type:Boolean, require:false, default:false},
    ready:{type:Boolean,default:false},
    served:{type:Boolean,default:false},
    paid:{type:Boolean, default:false},
    price: {type:Number, default:0},
    quantity: {type:Number,default:0},
    created_at: { type: Date, default: Date.now }

}

Payment Model

var mongoose = require('mongoose');

var PaymentSchema = new mongoose.Schema({
   order_number: {type:String, required: true, index: true},
   order_id: {type:mongoose.Schema.Types.ObjectId, ref: 'Orders'},
   date: { type: Date, default: Date.now },
   customer_id: {type:mongoose.Schema.Types.ObjectId, ref: 'User'},
   amount : { type: Number, required:true },
   company_id: {type:mongoose.Schema.Types.ObjectId, ref: 'Company'}
},
{
  toJSON: { virtuals: true },
  toObject: { virtuals: true }
});

module.exports = mongoose.model('Payments', PaymentSchema);

Here is my Code

var data = req.body;
var calls = [];
var local_orders = [];
var OrderModel = require('../models/Order');
var PaymentModel = require('../models/Payment');

OrderModel.find({'table_no': data.table_no}, function(err,orders){

    async.forEach(orders, function(vorders, callback){

        PaymentModel.find({order_id:vorders.id}, function(err, payments){
                vorders.payments = 'payments';
                    local_orders.push(vorders)
                });

                return callback(null, local_orders);

            }, function(err,local_orders){
                if(err){
                    res.status('500').send(err);
                }
                res.send(local_orders)
        });

})

I am expecting to receive a JSON Object like this, but i'm getting is undefined.

[{ menu_id: {type:mongoose.Schema.Types.ObjectId, ref: 'Foods'},
   menu_name: {type:String,required:false},
   user_id: {type:String,required: true,},
   customer_name:{type:String, required: false},
   table_no:{type:String,required:true},
   cooking:{type:Boolean, require:false, default:false},
   ready:{type:Boolean,default:false},
   served:{type:Boolean,default:false},
   paid:{type:Boolean, default:false},
   price: {type:Number, default:0},
   quantity: {type:Number,default:0},
   created_at: { type: Date, default: Date.now },
   payments : [{ payment1 },{ payment2 }
},...]

Please comment if you need more clarification or something is missing. Thank you! Cheers!

async.forEach callback does not provide data, you should use aysnc.map caolan.github.io/async/docs.html#each — Dhirendra
– Dhirendra, Commented Dec 6, 2016 at 8:58
i tried storing data from the query into a local variable, so that if the tasks are finished response data will be the local variable. is that correct? — android-guy
– android-guy, Commented Dec 6, 2016 at 9:18

chridam · Accepted Answer · 2016-12-06 09:41:24Z

1

The simplest and most efficient way of doing this simple task is by using the aggregation framework where you can leverage mongo's native operators like $match to filter the document stream to allow only matching documents to pass unmodified into the next pipeline stage and $lookup to perform a left outer join to the payment collection in the same database to filter in documents from the "joined" collection for processing:

var data = req.body;
OrderModel.aggregate([
    { "$match": { "table_no": data.table_no } },
    {
        "$lookup": {
            "from": "payments",
            "localField": "_id",
            "foreignField": "order_id",
            "as": "payments"
        }
    }
]).exec(function (err, result){
    if (err){
        res.status('500').send(err);
    }
    res.send(result)
});

However, as it stands your code is failing here

PaymentModel.find({ order_id: vorders.id }, function(err, payments){

since vorders object does not have any id key but _id, so that should be

PaymentModel.find({ "order_id": vorders._id }, function(err, payments){

edited Dec 6, 2016 at 9:41

answered Dec 6, 2016 at 9:14

chridam

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5 Comments

android-guy Over a year ago

Thanks! does order_id: "id" or order_id: ObjectId("id") make a difference? I can't make to seem it work. :)

android-guy Over a year ago

this answer is really straightforward and simple, i don't need to work with async to reach my requirement

chridam Over a year ago

You don't necessarily need to cast a string to ObjectIdin Mongoose as it does this implicitly for you ("behind the scenes")

android-guy Over a year ago

I see, i'm trying to implement your code, but i still get undefined. im not sure what to put with "from" in $lookup. i posted more details about the model and how it is required.

android-guy Over a year ago

so, it didn't worked because of the error. i didn't see the error until i debugged it in the browser.

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