Hi George, thanks for your feedback and thanks also for the link. Nice to see the faceting functionality in action.

Unfortunately with the API changes in version 5, I'm unable to make the upgrade without breaking all my faceting code.

What are your problems exactly?

Regarding the faceting rewrite. I am pretty much finished with switching from our custom FieldCache based solution, to Lucene's dynamic faceting using DocValues. In fact there is even a first pull request - https://github.com/hibernate/hibernate-search/pull/819. The faceting API is pretty much the same. The biggest difference is that now you have to explicitly configure the fields you are using for faceting using @Facet. Also values with zero counts are now per default not included and need to be explicitly enabled.