In this chapter, we saw the main concepts of the indexing phase in Solr. Being an inverted-index-based search engine, Solr strongly relies on the indexing phase by allowing a customizable and tunable index chain.

The Solr write path is a chain of responsibility consisting of several actors, each of them with a precise role in the overall process. While you must know, configure, and control those components as a user, you must also be aware of their high level of extensibility (as a developer). This allows you to adapt and eventually customize a Solr instance according to your specific needs.

We addressed the concepts that form the Solr data model, such as documents, core, schema, fields, and types. We also looked at the indexing configuration and the involved components such as update request processors, update chains, and request handlers. We finally described how to configure these components and write extensions on top of them.

The purpose of the indexing phase and the index itself is to optimize speed and performance in finding relevant documents during searches. Hence, the whole process is not useful without the search phase, which is the subject of the next chapter.