Class SortedSetDocValuesReaderState

Wraps a IndexReader and resolves ords using existing SortedSetDocValues APIs without a separate taxonomy index. This only supports flat facets (dimension + label), and it makes faceting a bit slower, adds some cost at reopen time, but avoids managing the separate taxonomy index. It also requires less RAM than the taxonomy index, as it manages the flat (2-level) hierarchy more efficiently. In addition, the tie-break during faceting is now meaningful (in label sorted order).

NOTE: creating an instance of this class is somewhat costly, as it computes per-segment ordinal maps, so you should create it once and re-use that one instance for a given IndexReader.