What is the best way to perform an inner join in MongoDB using Mongoose and NestJS?

Question

What is the best way to perform an inner join in MongoDB using Mongoose and NestJS?

I need to merge customer and product data in the same request from a system using Mongoose with MongoDB in Nest JS.

Here is an example of how the data is structured in the database:

  "_id": "621d2137abb45e60cf33a2d4",
        "product_id": [
            "621cedbf79d68fb4689ef0cb",
            "621cedbf79d68fb4689ef0cb",
            "621cedbf79d68fb4689ef0cb"
        ],
        "client_id": "621d19f890ec693f1d553eff",
        "price": 597,
        "__v": 0

Below is my service implementation:

  findAll() {
    return this.sealsModel.find().exec();
  }

I tried the following approach, but it didn't work as expected:

findAll() {
    var a = this.sealsModel.find().exec()
    return this.sealsModel.aggregate([{
        $lookup: {
          from: 'seals',
          localField: 'client_id',
          foreignField: '_id',
          as: 'client' 
        }
    }])            
    .exec()
}

The above method returned the following output:


 "_id": "621d3e0a1c3bcac85f79f7cc",
        "product_id": [
            "621cedbf79d68fb4689ef0cb",
            "621cedbf79d68fb4689ef0cb",
            "621cedbf79d68fb4689ef0cb"
        ],
        "client_id": "621d19f890ec693f1d553eff",
        "price": 597,
        "__v": 0,
        "client": []

javascript mongodb mongoose nestjs

Answer 1

Answer №1

Instead of using Mongo's $lookup operator, you can opt for Mongoose's populate function. To utilize it effectively, the first step is to update your model.

Your client model should resemble this:

// /models/Client.js
const mongoose = require("mongoose");

const clientSchema = mongoose.Schema({
  _id: mongoose.Schema.Types.ObjectId,
  ... // include your other fields here
});

module.exports = mongoose.model('Client', clientSchema);

The important detail to note is the reference name 'Client' used in the last line of the model.

You mainly need to make changes in your Seal model :

// /models/Seal.js
const mongoose = require("mongoose");

const sealSchema = mongoose.Schema({
  _id: mongoose.Schema.Types.ObjectId,
  client_id: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Client" // Same name as given to the client model above
  }
});

module.exports = mongoose.model('Seal', sealSchema);

Then, in your code, you can use:

const Seal = require("YOUR_PATH/models/Seal.js")

Seal.find().populate("client_id")

An important thing to remember is that your model represents the mongo ID as a string

"_id": "621d3e0a1c3bcac85f79f7cc",
"client_id": "621d19f890ec693f1d553eff", <---

Ensure that the field client_id is of type ObjectId or it will not function properly:

"client_id": ObjectId("621d19f890ec693f1d553eff")

Answer 2

Instead of using Mongo's $lookup operator, you can opt for Mongoose's populate function. To utilize it effectively, the first step is to update your model.

Your client model should resemble this:

// /models/Client.js
const mongoose = require("mongoose");

const clientSchema = mongoose.Schema({
  _id: mongoose.Schema.Types.ObjectId,
  ... // include your other fields here
});

module.exports = mongoose.model('Client', clientSchema);

The important detail to note is the reference name 'Client' used in the last line of the model.

You mainly need to make changes in your Seal model :

// /models/Seal.js
const mongoose = require("mongoose");

const sealSchema = mongoose.Schema({
  _id: mongoose.Schema.Types.ObjectId,
  client_id: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Client" // Same name as given to the client model above
  }
});

module.exports = mongoose.model('Seal', sealSchema);

Then, in your code, you can use:

const Seal = require("YOUR_PATH/models/Seal.js")

Seal.find().populate("client_id")

An important thing to remember is that your model represents the mongo ID as a string

"_id": "621d3e0a1c3bcac85f79f7cc",
"client_id": "621d19f890ec693f1d553eff", <---

Ensure that the field client_id is of type ObjectId or it will not function properly:

"client_id": ObjectId("621d19f890ec693f1d553eff")

What is the best way to perform an inner join in MongoDB using Mongoose and NestJS?

Answer №1

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