Is it possible to upgrade from Solr 5.x to Solr 8.x?

Question

Looking into upgrading our solar instance from version 5 to version 8.

I worked through the index upgrading tools but it doesn't allow upgrading an index create before version 7 into version 8.

Exception in thread "main" org.apache.lucene.index.IndexFormatTooOldException: Format version is not supported (resource BufferedChecksumIndexInput(MMapIndexInput(path="/var/solr/data/solr5_restore_test/data/snapshot.collection1.20201230023602/segments_4ya8s"))): This index was initially created with Lucene 6.x while the current version is 8.6.1 and Lucene only supports reading the current and previous major versions.. This version of Lucene only supports indexes created with release 7.0 and later.

I was wondering if there were any alternatives or if it would require reindexing everything.

Answer 1

You need to re-index the data with new version of Solr ie with version 8.

Its not advisable to upgrade though many versions. Solr supports the index formats of the immediate earlier versions.

Please check if the below tool help you achieve UpdateIndex

With the newer version sometimes, some of the field types are updated or removed. I would suggest get you your index ready by re-indexing the data with newer version of Solr. Once index is ready you can use it for your application.