4 Dec 2023, Apache Lucene™ 9.9.0 available

The Lucene PMC is pleased to announce the release of Apache Lucene 9.9.0.

Apache Lucene is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.

This patch release contains bug fixes that are highlighted below. The release is available for immediate download at:


Lucene 9.9.0 Release Highlights

New Features

  • Add int8 scalar quantization to the HNSW vector format. This optionally allows for more compact lossy storage for the vectors, requiring approximately 4x less memory for fast HNSW search.
  • HNSW graph now can be merged with multiple threads, leveraging the same infrastructure that inter-segment concurrency utilizes.


  • Speed up Panama vector support, use FMA, and test improvements.
  • FSTCompiler can now approximately limit how much RAM it uses to share suffixes during FST construction using the suffixRAMLimitMB method. 


  • Faster top-level conjunctions on term queries when sorting by descending score.
  • Change Postings back to using FOR in Lucene99PostingsFormat. Freqs, positions and offset keep using PFOR.

... plus a multitude of helpful bug fixes!

Further details of changes are available in the change log available at: http://lucene.apache.org/core/9_9_0/changes/Changes.html

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

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