public override SortedSetDocValues GetSortedSet(FieldInfo fieldInfo)
{
var field = FIELDS[fieldInfo.Name];
// SegmentCoreReaders already verifies this field is
// valid:
Debug.Assert(field != null);
var input = (IndexInput) DATA.Clone();
var scratch = new BytesRef();
return new SortedSetDocValuesAnonymousInnerClassHelper(this, field, input, scratch);
}