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)

User-defined functions


So far, we have only done simple SELECT operations that are inherently permitted by Cassandra. In the case of complex queries, where we could not fetch results based on just the primary key indexes, we built secondary indexes and materialized views. What if there arises a situation where you are required to perform some custom computations? Fortunately, Cassandra provides custom user-defined functions to perform some simple computations on the data present in Cassandra.

UDFs allow the execution of user code on the server side. The coordinator node takes care of the computation. In Cassandra 3.0 and later, UDFs are executed in a sandbox. You can also use custom security managers to prevent UDFs from accessing the filesystem or to prevent the execution of harmful code. Java and JavaScript are supported by default.

Note

Cassandra UDFs can be written in any language with JSR223 support. The list of languages includes Java, JavaScript, Ruby, and Python, among others. Though...