doc.add(new SortedSetDocValuesFacetField("a", "bar"));
writer.addDocument(config.build(doc));
doc = new Document();
doc.add(new SortedSetDocValuesFacetField("a", "baz"));
writer.addDocument(config.build(doc));
IndexSearcher searcher = newSearcher(writer.getReader());
FacetsCollector c = new FacetsCollector();