Apache Lucene is a high-performance, cross-platform, full-featured Information Retrieval library in open source, suitable for nearly every application that requires full-text search features.

Since its introduction nearly 10 years ago, Apache Lucene has become a competitive player for developing extensible, high-performance full-text search solutions. The experience accumulated over time by the community of Lucene committers and contributors and the innovations they have engineered have delivered significant ongoing advances in Lucene's capabilities.

This white paper describes the new features and improvements in the latest version, Apache Lucene 2.9. It is intended mainly for programmers familiar with the broad base of Lucene's capabilities, though those new to Lucene should also find it a useful exploration of the newest features.

In the simplest terms, Lucene is now faster and more flexible than before. Historic weak points have been improved to open the way for innovative new features like near-real-time search, flexible indexing, and high-performance numerical range queries. Many new features have been added, new APIs introduced, and critical bugs have been fixed - all with the same goal: improving Lucene's state-of-the-art search capabilities.