?? March 2022, Apache Lucene™ 9.1 available

The Lucene PMC is pleased to announce the release of Apache Lucene 9.1.

Apache Lucene is a high-performance, full-featured search engine library written entirely in Java. It is a technology suitable for nearly any application that requires structured search, full-text search, faceting, nearest-neighbor search on high-dimensionality vectors, spell correction or query suggestions.

This release contains numerous features, optimizations, and improvements, some of which are highlighted below. The release is available for immediate download at:

https://lucene.apache.org/core/downloads.html

Lucene 9.1 Release Highlights

New features

• Lucene JARs are now proper Java modules, with module descriptors and dependency information
• Support for filtering in nearest-neighbor vector search

• Support for intervals queries in the standard query syntax

• A new token filter SpanishPluralStemFilter for precise stemming of Spanish plurals

Optimizations

• Up to 30% improvement in index throughput for high-dimensional vectors 
• Up to 10% faster nearest neighbor searches on high-dimensional vectors
• Faster execution of "count" searches across different query types
• Faster counting for taxonomy facets
• Several other search speed-ups, including improvements to PointRangeQuery, MultiRangeQuery, and CoveringRangeQuery

Other

• The test framework is now a module, so all classes have been moved from to org.apache.lucene.tests.* to avoid package name conflicts
• Lucene now faithfully implements the HNSW algorithm for nearest neighbor search by supporting multiple graph layers

... plus a number of helpful bug fixes!

Further details of changes are available in the change log available at: (TODO: 9.1 changelog).

Please report any feedback to the mailing lists (http://lucene.apache.org/core/discussion.html)

Note: The Apache Software Foundation now uses a content distribution network (CDN) for distributing releases.