@Explain(vectorization = Vectorization.EXPRESSION, displayName = "projectedOutputColumnNums", explainLevels = { Level.DEFAULT, Level.EXTENDED })
    public String getProjectedOutputColumnNums() {
      return Arrays.toString(vectorGroupByDesc.getProjectedOutputColumns());
    }
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