Before going further into the book, we would like to emphasize that we are treating this book as an extension to the Elasticsearch Server Second Edition book we've written, also published by Packt Publishing. Of course, we start with a brief introduction to both Apache Lucene and Elasticsearch, but this book is not for a person who doesn't know Elasticsearch at all. We treat Mastering Elasticsearch as a book that will systematize your knowledge about Elasticsearch and extend it by showing some examples of how to leverage your knowledge in certain situations. If you are looking for a book that will help you start your journey into the world of Elasticsearch, please take a look at Elasticsearch Server Second Edition mentioned previously.

That said, we hope that by reading this book, you want to extend and build on basic Elasticsearch knowledge. We assume that you already know how to index data to Elasticsearch using single requests as well as bulk indexing. You should also know how to send queries to get the documents you are interested in, how to narrow down the results of your queries by using filtering, and how to calculate statistics for your data with the use of the faceting/aggregation mechanism. However, before getting to the exciting functionality that Elasticsearch offers, we think we should start with a quick tour of Apache Lucene, which is a full text search library that Elasticsearch uses to build and search its indices, as well as the basic concepts on which Elasticsearch is built. In order to move forward and extend our learning, we need to ensure that we don't forget the basics. This is easy to do. We also need to make sure that we understand Lucene correctly as Mastering Elasticsearch requires this understanding. By the end of this chapter, we will have covered the following topics: