Understanding luceneMatchVersion behavior after Fusion upgrade

Issue

After upgrading Fusion from version 5.9.4 to 5.9.10, the <luceneMatchVersion> value in solrconfig.xml for previously existing collections remains at 9.0, while newly created collections display 9.10. There is concern about whether the older version number impacts Solr functionality or poses any risk when operating with upgraded Fusion deployments.

Diagnosis

To confirm if this article addresses your scenario, check the <luceneMatchVersion> entry in the solrconfig.xml for your upgraded collections. If you observe that upgraded collections retain an older version number (for example, 9.0), but new collections use a newer version number (such as 9.10), this article is relevant.

Environment

Fusion 5.9.4, 5.9.5, and 5.9.10 (Kubernetes deployments, including AKS, EKS, GKE, and other platforms).

Cause

The <luceneMatchVersion> value in solrconfig.xml is intentionally preserved during upgrades to maintain backward compatibility for existing collections. This setting primarily affects certain Solr default behaviors and parsing options, not the underlying Lucene libraries used by Solr. Newly created collections use the default value for the current Fusion release, while upgraded collections retain their existing value unless manually changed.

Resolution

• The version specified in <luceneMatchVersion> within solrconfig.xml controls select Solr default behaviors for that collection, primarily to preserve backward compatibility.

• The actual Lucene libraries in use are determined by the Fusion and Solr version, not the solrconfig.xml entry.

• It is not required to update the <luceneMatchVersion> entry after a Fusion upgrade if there is a specific behavior of the older version you need.

• It is safe to continue operating with collections that have an older <luceneMatchVersion>, though plans to test and use the newer version number should be implemented.  It is best practice to validate your workload with standard application testing following any upgrade.

• If you choose to update the <luceneMatchVersion> for an existing collection, review the Solr documentation for impacts to parsing, analyzers, or query behavior, and thoroughly test before deploying to production.

Note: No further action is required unless you encounter a specific need to update Solr parsing behaviors for upgraded collections.