@Override
  public boolean isEqual(Object val1, Object val2) {
    if (val1 == null || val2 == null) {
      return (val1 == null && val2 == null);
    }
    Object[] v1 = (Object[]) val1;
    Object[] v2 = (Object[]) val2;

    assert v1.length == v2.length;
    for (int i = 0; i < v1.length; i++) {
      if (v1[i] == null && v2[i] == null) {
        continue;
      }
      if (v1[i] == null || v2[i] == null) {
        return false;
      }
      if (ObjectInspectorUtils.compare(
              v1[i], orderDef.getExpressions().get(i).getOI(),
              v2[i], orderDef.getExpressions().get(i).getOI()) != 0) {
        return false;
      }
    }
    return true;
  }
Simply returns the Object[] returned by VectorPTFGroupBatches.getAt(i), which contains the
value of the ordering columns.
ql/src/java/org/apache/hadoop/hive/ql/udf/ptf/ValueBoundaryScanner.java