We started the previous chapter by learning how to deal with revised filtering in Elasticsearch 2.x and what to expect from it now. We also explored highlighting and how it can help us in improving the users' search experience. We discovered query validation in Elasticsearch and learned the ways of data sorting in Elasticsearch. Finally, we discussed query rewriting and how that affects our queries. By the end of this chapter, you will have learned the following topics:
Indexing tree-like structures
Indexing data that is not flat
Handling document relationships by using nested object and parent–child features
Modifying index structure by using Elasticsearch API