Async: Combining two mongodb collection using Async.forEach - node.js

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!

Answer 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){