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From Michael McCandless <>
Subject Lucene 2.4.0 release
Date Sat, 11 Oct 2008 15:50:45 GMT

Release 2.4.0 of Lucene is now available!

With 2.4.0 we have relaxed the backwards compatibility policy of the
Fieldable interface: we now allow changes on a case by case basis.
This means any custom classes that implement Fieldable will need to be
updated.  This was done to accommodate the new omitTf() method (to do
pure boolean searching).

Many new features, fixes and optimizations have happened since 2.3,

   * New InstantiatedIndex (contrib/instantiated): RAM-based index that
     enables much faster searching than RAMDirectory.

   * New IndexWriter constructors now default autoCommit to false.

   * New commit() method in IndexWriter lets you control when changes
     are made visible and permanent in the index.

   * A machine or OS crash, or power loss, while IndexWriter is writing
     to an index will no longer corrupt the index.

   * TimeLimitedCollector adds timeout to searches.

   * Delete documents by Query in IndexWriter.

   * Pure boolean indexing (no frequency, positions nor payloads are
     indexed) using Field.setOmitTf().

   * A new Directory implementation, NIOFSDirectory, using java.nio's
     APIs to allow multiple threads to read from the same open file
     without locking.

   * IndexWriter.expungeDeletes() reclaims disk space from deleted
     documents by merging away segments that have deletions.

   * All filters now return a DocIdSet instead of java.util.BitSet,
     making filters more efficient and flexible.

   * Searching with a Filter is more efficient: now the filter is
     applied to a document before scoring is done.

   * IndexReader can be opened with new readOnly=true mode, which gives
     better performance in a multi-threaded environment.

The detailed changes are here:

Lucene 2.4.0 includes index format changes that are not readable by  
versions of Lucene.  Lucene 2.4.0 can both read and update older Lucene
indexes.  Adding to an index with an older format will cause it to be
converted to the newer format.

Binary and source distributions are available at

Lucene artifacts are also available in the Maven2 repository at


The next release will be 2.9.  After that will be 3.0, which will
remove all deprecated APIs from 2.9 and will be the first release of
Lucene to require JRE 1.5.  The timing on these two releases is not
yet known.


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