Schema versioning strategies in MongoDB - Mini Project: Build & Apply

Schema Versioning Strategies in MongoDB

📖 Scenario: You work for a company that stores user profiles in a MongoDB collection. Over time, the profile structure changes as new features are added. You need to manage different versions of the user profile schema to keep the data consistent and allow smooth upgrades.

🎯 Goal: Build a MongoDB document structure that includes a schema version field and write queries to handle documents based on their schema version.

📋 What You'll Learn

Create a MongoDB collection with user profile documents including a schemaVersion field.

Add a configuration variable to represent the current schema version.

Write a query to find all user profiles with an older schema version.

Write a query to update user profiles to the latest schema version.

💡 Why This Matters

🌍 Real World

Managing schema versions in MongoDB helps keep data consistent as applications evolve and new features require changes to data structure.

💼 Career

Database developers and administrators often need to handle schema migrations and versioning to ensure smooth application upgrades and data integrity.

1

Create initial user profiles with schema version

Create a MongoDB collection called userProfiles and insert three documents with the exact fields: name, email, and schemaVersion. Use these exact values: { name: "Alice", email: "[e-mail]", schemaVersion: 1 }, { name: "Bob", email: "[e-mail]", schemaVersion: 1 }, { name: "Charlie", email: "[e-mail]", schemaVersion: 2 }.

MongoDB

// Insert the three user profile documents with schemaVersion
// Your code here

Need a hint?

Use insertMany to add multiple documents to the userProfiles collection.

2

Set current schema version variable

Create a variable called currentSchemaVersion and set it to the number 2 to represent the latest schema version.

MongoDB

db.userProfiles.insertMany([
  { name: "Alice", email: "[e-mail]", schemaVersion: 1 },
  { name: "Bob", email: "[e-mail]", schemaVersion: 1 },
  { name: "Charlie", email: "[e-mail]", schemaVersion: 2 }
])

// Create currentSchemaVersion variable
// Your code here

Need a hint?

Use const to declare the variable currentSchemaVersion and assign it the value 2.

3

Query user profiles with older schema versions

Write a MongoDB query to find all documents in userProfiles where schemaVersion is less than currentSchemaVersion. Use the variable currentSchemaVersion in your query.

MongoDB

db.userProfiles.insertMany([
  { name: "Alice", email: "[e-mail]", schemaVersion: 1 },
  { name: "Bob", email: "[e-mail]", schemaVersion: 1 },
  { name: "Charlie", email: "[e-mail]", schemaVersion: 2 }
])

const currentSchemaVersion = 2

// Find user profiles with schemaVersion less than currentSchemaVersion
// Your code here

Need a hint?

Use find with a query object that uses $lt to compare schemaVersion with currentSchemaVersion.

4

Update old user profiles to latest schema version

Write a MongoDB update query to set the schemaVersion field to currentSchemaVersion for all documents in userProfiles where schemaVersion is less than currentSchemaVersion. Use updateMany.

MongoDB

db.userProfiles.insertMany([
  { name: "Alice", email: "[e-mail]", schemaVersion: 1 },
  { name: "Bob", email: "[e-mail]", schemaVersion: 1 },
  { name: "Charlie", email: "[e-mail]", schemaVersion: 2 }
])

const currentSchemaVersion = 2

const oldProfiles = db.userProfiles.find({ schemaVersion: { $lt: currentSchemaVersion } })

// Update old profiles to currentSchemaVersion
// Your code here

Need a hint?

Use updateMany with a filter for documents with older schema versions and set their schemaVersion to currentSchemaVersion.