Existing Elasticsearch data incompatible with Hippo13

While attempting to upgrade from Hippo12 to Hippo13, one of the problems we encounter is with elasticsearch. We are using the relevance module, and this stores information about
visits in an Elasticsearch index. We are using elasticsearch major version 6 (both for or current production environment running Hippo12 and for the local development environment).

The problem is that Hippo13 complains that the storage version reported by the elasticsearch index is not compatible with Hippo13. I have been able to trace the source of this incompatibility to the method

TargetingMappings.determineCompatibleVersionKeys()

This method creates a hardcoded list of Regex matchers to determine which old versions of the elasticsearch indexed data are compatible with the new Hippo13 version.

Curiously enough, this method adds matchers for Hippo version 10, 11 and 13, but not for 12.

My questions are these:

1 Is my interpretation of what happens correct, that there are no version matchers in Hippo13
that will match data indexed with Hippo12?

2 How do I solve my problem? Converting the data currently stored by Hippo12 to a format
compatible with Hippo13 would be an option, but I have no idea where to start or how much
work this would be.

Before we only supported Elasticsearch 5 with release 12 and the hippo11/elastic5 version was kept for the Elasticsearch mapping as the mapping did not change between releases. The upgrade to release 13 should not be much work. Please contact support so we can help you with this case. I created BT-2171 to enhance the upgrade steps

This problem is solved in release 13.4.1 of brmx. It was indeed a question of a missing case in the code for TargetMappings, just as I suggested.