code: public void flush() throws ExecutionException, InterruptedException {
          for (int i = m_firstPartitionTable; i <= m_lastPartitionTable; i++) {
              m_partitionTable[i].flushAllTableQueues();
          }
      }
docs: Called to asynchronously force the VoltBulkLoader to submit all the partially full batches
  in all partitions of the table to the Client for insert. To wait for all rows to be processed,
  use drain(). This method will also flush pending rows submitted by other VoltBulkLoader
  instances working on the same table and using the same instance of Client.