Book Image

Learning Apache Cassandra - Second Edition

Book Image

Learning Apache Cassandra - Second Edition

Overview of this book

Cassandra is a distributed database that stands out thanks to its robust feature set and intuitive interface, while providing high availability and scalability of a distributed data store. This book will introduce you to the rich feature set offered by Cassandra, and empower you to create and manage a highly scalable, performant and fault-tolerant database layer. The book starts by explaining the new features implemented in Cassandra 3.x and get you set up with Cassandra. Then you’ll walk through data modeling in Cassandra and the rich feature set available to design a flexible schema. Next you’ll learn to create tables with composite partition keys, collections and user-defined types and get to know different methods to avoid denormalization of data. You will then proceed to create user-defined functions and aggregates in Cassandra. Then, you will set up a multi node cluster and see how the dynamics of Cassandra change with it. Finally, you will implement some application-level optimizations using a Java client. By the end of this book, you'll be fully equipped to build powerful, scalable Cassandra database layers for your applications.
Table of Contents (14 chapters)

A normalized approach


Before we proceed down the path of denormalization, let's first try an approach that requires adding no new tables to our schema. Our goal is to display to a user all the status updates of all the users they follow, the most recent first. So, the simplest approach would be to simply look up the followed users and then retrieve their status updates.

If you've been following along with the code examples so far, you should currently have a single follow relationship in the database, such as alice follows carol. To make things more interesting, let's also have alice follow dave:

INSERT INTO "user_outbound_follows" 
  ("follower_username", "followed_username") 
VALUES ('alice', 'dave'); 

INSERT INTO "user_inbound_follows" 
  ("followed_username", "follower_username") 
VALUES ('dave', 'alice');

Now that alice is following a couple of users, we can build a meaningful home timeline for her. Let's have carol and dave write some updates:

INSERT INTO "user_status_updates" ("username...