for(int i = atLeast(30); i > 0; --i) {
Document doc = new Document();
doc.add(new StringField("f", "v", Field.Store.NO));
doc.add(new FacetField("a", "1"));
doc.add(new FacetField("b", "1"));
iw.addDocument(config.build(taxoWriter, doc));
}
DirectoryReader r = DirectoryReader.open(iw, true);
DirectoryTaxonomyReader taxoReader = new DirectoryTaxonomyReader(taxoWriter);