We have seen how to index data from a standard file format such as JSON or XML. But what about proprietary file formats such as Word and PDF? Luckily, Solr comes to the rescue with the use of the Apache Tika project. The Tika framework provides a way to incorporate various file formats such as Word and PDF. 

Internally, Tika uses the Apache PDFBox parser to parse PDF and Apache POI for the Word format. Solr provides ExtractingRequestHandler, which makes use of Tika to upload binary files and to index as well as extract data.

This framework in Solr is known as Solr Cell, which is an abbreviation of Solr content extraction library, the name when this framework was under development.