@Explain(vectorization = Vectorization.OPERATOR, displayName = "vectorProcessingMode", explainLevels = { Level.DEFAULT, Level.EXTENDED })
    public String getProcessingMode() {
      return vectorGroupByDesc.getProcessingMode().name();
    }
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