- Multiple paths per document
- Query-time analysis of the facet-field; no special requirements for indexing besides retaining separator characters in the terms used for faceting
- Optional custom sorting of tag values
- Recursive counting of references to tags at all levels of the output
This is a shell around LUCENE-2369, making it work with the Solr API. The underlying principle is to reference terms by their ordinals and create an index wide documents to tags map, augmented with a compressed representation of hierarchical levels.