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4 Dec 2023, Apache Lucene™ 9.9.0 available

<work in progress>

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

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

httphttps://lucene.apache.org/core/mirrors-core-latest-redirdownloads.html

Lucene 9.

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9.0 Release Highlights

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• Make TaskExecutor constructor public and use TaskExecutor for concurrent HNSW graph build. (Shubham Chaudhary)

New Features

• Add int8 scalar quantization to the HNSW vector format. This optionally allows for more compact lossy storage lossy storage for the vectors, requiring about 75% approximately 4x less memory for fast HNSW search. (Ben Trent)

• HNSW graph now can be merged with multiple

thread. (Patrick Zhai)

Improvements

• threads, leveraging the same infrastructure that inter-segment concurrency utilizes.

Improvements

• Create a TaskExecutor when an executor is not provided to the IndexSearcher, in order to simplify consumer's code (Luca Cavanna)
• Speed up Panama vector support, use FMA, and test improvements. (Uwe Schindler, Robert Muir)
• FSTCompiler can now approximately limit how much RAM it uses to share
    suffixes during FST construction using the suffixRAMLimitMB method. (Mike McCandless)

Optimizations

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

... 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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