Dear All, On 19 Mar 2025, at 11:08, Jan Høydahl wrote:
Normally we recommend not to "upgrade" your existing nodes on a major upgrade, but instead stand up a clean new 9.x cluster/server and do a full re-index.
I second that. We did a similar upgrade recently (from a stand-alone 8.5.2 to SolrCloud 9.8.1), so I think I can share a few tips:
1. Very likely, you will need to upgrade your configuration files and port (merge) any existing modifications into the 9.8.1 default configuration file. This alone is a good reason to start fresh with a new install IMHO.
2. Re: full re-index, please note that the source can be the your existing 8.11 node. Instead of trying to copy and upgrade the Lucene index files, you can do a “logical” transfer, meaning that you can create a client script to read data from the source Solr in JSON format in batches of, say, 500-1000 documents each and feed those documents into the destination Solr as a regular INSERT. It is quite a robust method as any indexing errors will be immediately visible.
3. The re-indexing will also allow you to apply changes in the schema if needed (e.g. some fields might benefit from using DocValues).
My 2 cents :-) Kind regards, Corrado
