Book Image

Apache Cassandra Essentials

By : Nitin Padalia
Book Image

Apache Cassandra Essentials

By: Nitin Padalia

Overview of this book

Apache Cassandra Essentials takes you step-by-step from from the basics of installation to advanced installation options and database design techniques. It gives you all the information you need to effectively design a well distributed and high performance database. You’ll get to know about the steps that are performed by a Cassandra node when you execute a read/write query, which is essential to properly maintain of a Cassandra cluster and to debug any issues. Next, you’ll discover how to integrate a Cassandra driver in your applications and perform read/write operations. Finally, you’ll learn about the various tools provided by Cassandra for serviceability aspects such as logging, metrics, backup, and recovery.
Table of Contents (14 chapters)
Apache Cassandra Essentials
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Read operations


When a client requests data from a coordinator node, the coordinator node sends that request to all replica nodes responsible for owning the data. Replica nodes fetch data and respond to the coordinator node; the coordinator node then compares this data and responds to the client with the most recent data returned by the replicas.

A replica node may return data from a cache called row cache, or it might need to consult the SSTable and give merged data from both Memtable and SSTable.

Reads from row cache

A row cache is an off-heap cache that caches frequently accessed rows. It is configured at column family level and is optional. It caches complete or partial partition rows. In previous versions of Cassandra, it used to store complete the partition key row; however, in the 2.1 release, we can also configure how many clustering rows for a partition key should be cached. For example, the following CREATE statement will cache the latest 10 status updates from a user:

CREATE TABLE...