@Override
    public void setNextVectorBatchGroupStatus(boolean isLastGroupBatch) throws HiveException {
      // Do nothing.
    }
Global aggregates (no GROUP BY clause, no keys)
This mode is very simple, there are no keys to consider, and only flushes one row at closing
The one row must flush even if no input was seen (NULLs)
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorGroupByOperator.java