Hi all, there is quite a list of changes: http://people.apache.org/~rmuir/staging_area/lucene_solr_4_9_0_r1604085/l... some are good and nice bugfixes, but there is yet again quite a list of API / behaviour changes which affect us: - AttributeSource API - Directory API (requires Infinispan updates first) - MergePolicy API (we have our custom ones) - IndexWriter.delete methods changed - DocIdSet changed interface hierarchy - IndexWriterConfig no longer supports cloning, we'll need an efficient factory to rebuild these - IOContext has been added to various methods as mandatory parameter I'm overall not happy to see so many changes, but I believe we need to keep up so my vote is to upgrade. The best reason is a method drop in the Directory API, which is no longer needed, and was making it very hard to squeeze reasonable performance out of Infinispan. This method being gone now is very welcome: it required us to do double-buffering to implement the checksum functionality which was introduced in Lucene 4.8. Sanne