private void changeToStreamingMode() throws HiveException {
    processingMode = this.new ProcessingModeStreaming();
    processingMode.initialize(null);
    LOG.info("switched to streaming mode");
  }
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