Understanding the querying process

After reading the previous section, we now know how querying works in Elasticsearch. You know that Elasticsearch, in most cases, needs to scatter the query across multiple nodes, get the results, merge them, fetch for relevant documents, and return the results. What we didn't talk about is three additional things that define how queries behave: query rewrite, search type, and query execution preference. We will now concentrate on these functionalities of Elasticsearch and also try to show you how querying works.

Query logic

Elasticsearch is a distributed search engine, and so all functionality provided must be distributed in its nature. It is exactly the same with querying. Since we want to discuss some more advanced topics on how to control the query process, we first need to know how it works.

By default, if we don't alter anything, the query process will consist of two phases as shown in the following diagram:

When we send a query, we send it to one of the...