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XX November 2021, Apache Lucene™ 9.0 available

The Lucene PMC is pleased to announce the release of Apache Lucene 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 release contains numerous features, optimizations, and improvements, some of which are highlighted below. The release is available for immediate download at:

http://lucene.apache.org/core/mirrors-core-latest-redir.html

Lucene 9.0 Release Highlights

System requirements

  • Lucene 9.0 requires JDK 11 or newer

New features

  • Support for indexing high-cardinality numeric vectors to perform nearest-neighbor search, using the Hierarchical Navigable Small World graph algorithm.

File formats

  • File formats have all been changed from big-endian order to little endian order.

Optimizations

  • Lucene 9 takes advantage of Java VarHandles, introduced in Java 9, to speed up indexing and some queries.
  • Lucene now enforces that a field has the same schema across all documents in order to enable optimizations that take advantage of the index by default.
  • ConcurrentMergeScheduler now assumes fast I/O, likely improving indexing speed in case where heuristics would incorrectly detect whether the system had fast I/O or not.
  • Encoding of postings lists changed from FOR-delta to PFOR-delta.

Other

Further details of changes are available in the change log available at: http://lucene.apache.org/core/9_0/changes/Changes.html

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. We think it's unlikely, but the system is new, and it is possible that some glitch may cause the mirror you are using to lack the new release. If that is the case, please try another mirror. This also applies to Maven access.

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