if(valueFieldData == null)
_collector = new DistinctCollector(keyFieldData, distinctFieldData, tzRounding, exactThreshold);
else
throw new FacetPhaseExecutionException("unknown date_facet", "Can't use distinct_field and value_field together");
else if(valueFieldData == null)
_collector = new SlicedDistinctCollector(keyFieldData, sliceFieldData, distinctFieldData, tzRounding, exactThreshold);
else
throw new FacetPhaseExecutionException("unknown date_facet", "Can't use distinct_field and value_field together");
}