Lucene 9.1.0 facet API

Provides faceted indexing and search capabilities. Checkout this and this blog posts for some overview on the facets module as well as source code examples here.
Faceted search.
Provides range faceting capabilities.
Provides faceting capabilities over facets that were indexed with SortedSetDocValuesFacetField.
Taxonomy of Categories.
Taxonomy index implementation using on top of a Directory.
Improves indexing time by caching a map of CategoryPath to their Ordinal.