Lucene provides a text engine search library written in in Java. “Lucene users are people who need to add search to their apps,” says Simon Willnauer, a core committer on Lucene since 2006. Lucene is being used in Twitter, he notes, and began in 1997 when many companies were working on search.
Lucene 4.0 was released this past October, serving as a rewrite and supporting users’ own codecs for determining how data structures are encoded. This enables specialized use cases, Willnauer says. Lucene 4.1 was released in January, featuring disk space savings and performance improvements. Version 4.2, due in a few months, is expected to feature a refactoring of doc values capabilities for searching documents.