Partial indexes with filter in MongoDB - Mini Project: Build & Apply

Creating and Using Partial Indexes with Filters in MongoDB

📖 Scenario: You are managing a MongoDB collection that stores information about books in a library. Some books are currently available for borrowing, while others are checked out. You want to speed up queries that find only the available books by creating a partial index that includes only those books.

🎯 Goal: Build a MongoDB partial index on the books collection that indexes only the documents where the available field is true. This will help queries that search for available books run faster.

📋 What You'll Learn

Create a books collection with specific book documents

Add a filter condition variable for the partial index

Create a partial index on the available field with the filter

Verify the partial index creation command includes the filter correctly

💡 Why This Matters

🌍 Real World

Partial indexes help speed up queries by indexing only relevant documents, saving space and improving performance in large databases.

💼 Career

Database administrators and backend developers use partial indexes to optimize query speed and resource usage in real-world applications.

1

Create the books collection with sample documents

Create a books collection and insert these exact documents: { title: "The Hobbit", author: "J.R.R. Tolkien", available: true }, { title: "1984", author: "George Orwell", available: false }, and { title: "To Kill a Mockingbird", author: "Harper Lee", available: true }.

MongoDB

// Insert the specified documents into the books collection
// Your code here

Need a hint?

Use db.books.insertMany() with an array of the three book objects exactly as given.

2

Define the filter condition for the partial index

Create a variable called filterCondition that holds the filter { available: true } to use for the partial index.

MongoDB

db.books.insertMany([
  { title: "The Hobbit", author: "J.R.R. Tolkien", available: true },
  { title: "1984", author: "George Orwell", available: false },
  { title: "To Kill a Mockingbird", author: "Harper Lee", available: true }
])

// Define the filterCondition variable with the filter for available books
// Your code here

Need a hint?

Use const filterCondition = { available: true } to define the filter.

3

Create the partial index using the filter condition

Use db.books.createIndex() to create an index on the available field with the partial filter expression set to the filterCondition variable.

MongoDB

db.books.insertMany([
  { title: "The Hobbit", author: "J.R.R. Tolkien", available: true },
  { title: "1984", author: "George Orwell", available: false },
  { title: "To Kill a Mockingbird", author: "Harper Lee", available: true }
])

const filterCondition = { available: true }

// Create a partial index on the available field using filterCondition
// Your code here

Need a hint?

Use db.books.createIndex({ available: 1 }, { partialFilterExpression: filterCondition }) to create the partial index.

4

Confirm the partial index creation command includes the filter

Add a command to list all indexes on the books collection using db.books.getIndexes() to verify the partial index was created with the filter.

MongoDB

db.books.insertMany([
  { title: "The Hobbit", author: "J.R.R. Tolkien", available: true },
  { title: "1984", author: "George Orwell", available: false },
  { title: "To Kill a Mockingbird", author: "Harper Lee", available: true }
])

const filterCondition = { available: true }

db.books.createIndex({ available: 1 }, { partialFilterExpression: filterCondition })

// List all indexes on the books collection to verify the partial index
// Your code here

Need a hint?

Use db.books.getIndexes() to see all indexes on the collection.