Hello! I suppose the only way to make this work will be reindexing the data. Solr 4.1 uses Lucene 4.1 as you know, which introduced new default codec with stored fields compression and this is one of the reasons you can't read that index with 4.0.
-- Regards, Rafał Kuć Sematext :: http://sematext.com/ :: Solr - Lucene - Nutch - ElasticSearch > Solr 4.1 has been giving up much trouble rejecting documents indexed. > While I try to work my way through this, I would like to move our > application back to Solr 4.0. However, now when I try to start Solr > with same index that was created with Solr 4.0 but has been running on > 4.1 few a few days I get this error chain: > org.apache.solr.common.SolrException: Error opening new searcher > Caused by: org.apache.solr.common.SolrException: Error opening new searcher > Caused by: java.lang.IllegalArgumentException: A SPI class of type > org.apache.lucene.codecs.Codec with name 'Lucene41' does not exist. > You need to add the corresponding JAR file supporting this SPI to your > classpath.The current classpath supports the following names: > [Lucene40, Lucene3x] > Obviously I'll not be installing Lucene41 in Solr 4.0, but is there > any way to work around this? Note that neither solrconf.xml nor > schema.xml have changed. Thanks.