Book Image

Elasticsearch Server - Third Edition

By : Rafal Kuc
Book Image

Elasticsearch Server - Third Edition

By: Rafal Kuc

Overview of this book

ElasticSearch is a very fast and scalable open source search engine, designed with distribution and cloud in mind, complete with all the goodies that Apache Lucene has to offer. ElasticSearch’s schema-free architecture allows developers to index and search unstructured content, making it perfectly suited for both small projects and large big data warehouses, even those with petabytes of unstructured data. This book will guide you through the world of the most commonly used ElasticSearch server functionalities. You’ll start off by getting an understanding of the basics of ElasticSearch and its data indexing functionality. Next, you will see the querying capabilities of ElasticSearch, followed by a through explanation of scoring and search relevance. After this, you will explore the aggregation and data analysis capabilities of ElasticSearch and will learn how cluster administration and scaling can be used to boost your application performance. You’ll find out how to use the friendly REST APIs and how to tune ElasticSearch to make the most of it. By the end of this book, you will have be able to create amazing search solutions as per your project’s specifications.
Table of Contents (18 chapters)
Elasticsearch Server Third Edition
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Introduction to Apache Lucene scoring


When talking about queries and their relevance, we can't omit the information about the scoring and where it comes from. But what is a score? The score is a property that describes the relevance of a document in the context of a query. In the following section, we will talk about the default Apache Lucene scoring mechanism – the TF/IDF algorithm and how it affects the returned document.

Note

The TF/IDF is not the only available algorithm exposed by Elasticsearch. For more information about the available models, refer to the Available similarity models section in Chapter 2, Indexing Your Data. You can also refer to the books Mastering Elasticsearch and Mastering Elasticsearch Second Edition published by Packt Publishing.

When a document is matched

When a document is returned by Lucene, it means that it matched the query we sent to it. In most cases, each of the resulting documents in the response is given a score. The higher the score, the more relevant the...