code: @Override
    public int getCompareValueType() throws IOException {
      switch (sortType) {
      case CodecUtil.STATS_TYPE_N:
        return 0;
      case CodecUtil.STATS_TYPE_SUM:
        return 1;
      case CodecUtil.STATS_TYPE_MAX:
        return 1;
      case CodecUtil.STATS_TYPE_MIN:
        return 1;
      case CodecUtil.STATS_TYPE_SUMSQ:
        return 1;
      case CodecUtil.STATS_TYPE_SUMOFLOGS:
        return 2;
      case CodecUtil.STATS_TYPE_MEAN:
        return 2;
      case CodecUtil.STATS_TYPE_GEOMETRICMEAN:
        return 2;
      case CodecUtil.STATS_TYPE_STANDARDDEVIATION:
        return 2;
      case CodecUtil.STATS_TYPE_VARIANCE:
        return 2;
      case CodecUtil.STATS_TYPE_POPULATIONVARIANCE:
        return 2;
      case CodecUtil.STATS_TYPE_QUADRATICMEAN:
        return 2;
      default:
        throw new IOException("sortType " + sortType + " not supported");
      }
    }
docs: /*
  (non-Javadoc)
  
  @see mtas.codec.util.collector.MtasDataItem#getCompareValueType()