@VisibleForTesting
    int getMaxHtEntries() {
      return maxHtEntries;
    }
Adjust for grouping sets. For grouping sets, input records are processed 'n' number of times.
Ref processBatch(). Ensure that reduction is super effective, otherwise they become
memory intensive.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorGroupByOperator.java