Lucene enhancements include the addition of a suggest/auto-complete function in the spell checker module, a less aggressive stemmer for English called KStem and the ability to merge results from multiple shards. Solr sees improvements which make use of the Lucene enhancements with a KStemFilterFactory, new suggest/autocomplete implementation “offering an order of magnitude smaller RAM consumption” and a new, more efficient merge policy used by default.
Both updates also include bug fixes and other modifications. Consult the Lucene CHANGES.TXT and Solr CHANGES.TXT files for complete details. The source code to Lucene and Solr are available for downloading from a number of mirror sites. Lucene and Solr are licensed under the Apache Licence V2.