: I got the following error when try to launch solr in tomcat after applying : patch SOLR-284
: java.lang.RuntimeException: org.apache.lucene.index.CorruptIndexException: : Unknown format version: -4 at org.apache.solr.core.SolrCore.getSearcher( that error indicates that the version of lucene you are using is incapable of opening indexes created by the version of lucene that created your index. specificly: i'm pretty sure -4 is the format version for Lucene 2.3.X did you by any chance apply the patch to an old version of Solr that was using Lucene 2.2 and then run it against an index you'd already made with a newer version of Solr? -Hoss
