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)

Retrieving status updates for a specific time range


Having explored the limits of the WHERE keyword in CQL, let's return to the user_status_updates table. Suppose we'd like to build an archive feature for MyStatus that displays all of the user's status updates for a requested month. In CQL terms, we want to select a range of clustering columns; for instance, let's get back all of alice's status updates created in May 2014:

SELECT "id", DATEOF("id"), "body"
FROM "user_status_updates"
WHERE "username" = 'alice'
AND "id" >= MINTIMEUUID('2014-05-01')
AND "id" <= MAXTIMEUUID('2014-05-31');

Before diving into the mechanics of this query, we can confirm that the only status update is the one with a UUID that was provided in the previous chapter, and was generated on May 29:

Creating time UUID ranges

In the preceding query, we encounter two new CQL functions: MINTIMEUUID and MAXTIMEUUID. These functions form perhaps the most powerful components of Cassandra's toolkit for working with timestamp...