Welcome to Mastering Elasticsearch 5.x, Third Edition. Elasticsearch has progressed rapidly from version 1.x, released in 2014, to version 5.x, released in 2016. During the two-and-a-half-year period since 1.0.0, adoption has skyrocketed, and both vendors and the community have committed bug-fixes, interoperability enhancements, and rich feature upgrades to ensure Elasticsearch remains the most popular NoSQL storage, indexing, and search utility for both structured and unstructured documents, as well as gaining popularity as a log analysis tool as part of the Elastic Stack.

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 Essentials, also published by Packt.

Before going further into the book, we assume that you already know the basic concepts of Elasticsearch for performing operations such as how to index documents, how to send queries to get the documents you are interested in, how to narrow down the results of your queries by using filters, and how to calculate statistics for your data with the use of the aggregation mechanism. However, before getting to the exciting functionality that Elasticsearch offers, we think we should start with a quick overview of Apache Lucene, which is a full text search library that Elasticsearch uses to build and search its indices. 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: