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...