@Explain(vectorization = Vectorization.OPERATOR, displayName = "Group By Vectorization", explainLevels = { Level.DEFAULT, Level.EXTENDED })
  public GroupByOperatorExplainVectorization getGroupByVectorization() {
    VectorGroupByDesc vectorGroupByDesc = (VectorGroupByDesc) getVectorDesc();
    if (vectorGroupByDesc == null) {
      return null;
    }
    return new GroupByOperatorExplainVectorization(this, vectorGroupByDesc);
  }
Checks if this grouping is like distinct, which means that all non-distinct grouping
columns behave like they were distinct - for example min and max operators.
ql/src/java/org/apache/hadoop/hive/ql/plan/GroupByDesc.java