@Override
  public void process(Object row, int tag) throws HiveException {
    VectorizedRowBatch batch = (VectorizedRowBatch) row;
    if (batch.size > 0) {
      processingMode.processBatch(batch);
    }
  }
changes the processing mode to streaming
This is done at the request of the hash agg mode, if the number of keys
exceeds the minReductionHashAggr factor
@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorGroupByOperator.java