ObjectId and how it is generated in MongoDB - Mini Project: Build & Apply

Understanding ObjectId and How It Is Generated in MongoDB

📖 Scenario: You are working on a simple MongoDB database for a small online store. Each product needs a unique identifier that MongoDB automatically generates. This identifier is called ObjectId. You want to learn how to create documents with ObjectId and understand its structure.

🎯 Goal: Build a MongoDB collection with documents that use ObjectId as their unique identifier. Learn how ObjectId is generated and how to access its components.

📋 What You'll Learn

Create a MongoDB collection named products with documents containing _id as ObjectId

Insert a document with specific fields: name and price

Extract and display the timestamp part of the ObjectId

Understand the components of ObjectId by accessing its properties

💡 Why This Matters

🌍 Real World

ObjectId is used in MongoDB to uniquely identify documents and embed creation time information, which helps in tracking when data was added.

💼 Career

Understanding ObjectId is essential for database developers and administrators working with MongoDB to manage data efficiently and perform time-based queries.

1

Create a products collection and insert a document with ObjectId

Create a MongoDB collection called products and insert one document with the fields name set to 'Laptop' and price set to 1200. Do not specify the _id field; MongoDB will generate an ObjectId automatically.

MongoDB

// Insert a document into the products collection
// Your code here

Need a hint?

Use insertOne on db.products with the document containing name and price.

2

Retrieve the inserted document and store its _id in a variable

Write a query to find the document where name is 'Laptop' and store its _id field in a variable called productId.

MongoDB

db.products.insertOne({ name: 'Laptop', price: 1200 })
// Find the document with name 'Laptop' and store its _id in productId
// Your code here

Need a hint?

Use findOne to get the document and then access its _id property.

3

Extract the timestamp from the ObjectId

Use the getTimestamp() method on the productId variable to get the creation time of the ObjectId and store it in a variable called creationTime.

MongoDB

db.products.insertOne({ name: 'Laptop', price: 1200 })
const product = db.products.findOne({ name: 'Laptop' })
const productId = product._id
// Get the timestamp from productId and store in creationTime
// Your code here

Need a hint?

Call getTimestamp() on productId to get the creation date.

4

Access the ObjectId components and complete the document with a new field

Add a new field called createdAt to the products collection document with the value of creationTime. Use updateOne with the _id equal to productId to set this field.

MongoDB

db.products.insertOne({ name: 'Laptop', price: 1200 })
const product = db.products.findOne({ name: 'Laptop' })
const productId = product._id
const creationTime = productId.getTimestamp()
// Update the document to add createdAt field with creationTime
// Your code here

Need a hint?

Use updateOne with a filter on _id and the $set operator to add the createdAt field.