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.

Packages

Package	Description
org.apache.lucene.facet	Faceted search.
org.apache.lucene.facet.range	Provides range faceting capabilities.
org.apache.lucene.facet.sortedset	Provides faceting capabilities over facets that were indexed with SortedSetDocValuesFacetField.
org.apache.lucene.facet.taxonomy	Taxonomy of Categories.
org.apache.lucene.facet.taxonomy.directory	Taxonomy index implementation using on top of a Directory.
org.apache.lucene.facet.taxonomy.writercache	Improves indexing time by caching a map of CategoryPath to their Ordinal.