xapian-doc binary package in Ubuntu Lunar amd64

 This package contains general documentation about Xapian, and more detailed
 API documentation.
 .
 The Xapian search engine library is a highly adaptable toolkit which allows
 developers to easily add advanced indexing and search facilities to their own
 applications. It implements the probabilistic model of information retrieval,
 and provides facilities for performing ranked free-text searches, relevance
 feedback, phrase searching, boolean searching, stemming, and simultaneous
 update and searching. It is highly scalable, and is capable of working with
 collections containing hundreds of millions of documents.

Source package