See org.hibernate.search.v6poc.backend.elasticsearch.document.model.impl.AbstractScalarFieldTypedContext#contribute in particular.

Field-level compression is deprecated. We should use index-level compression codecs instead.
In Elasticsearch, those are part of the index settings, so they are none of our business (they should be configured by the user).
In Lucene, we should provide a sensible default (maybe align with Elasticsearch?) and offer configuration properties to configure it.