private VectorizedRowBatch getCurrentBatch() {
      if (null == currentBatch) {
        currentBatch = produceNextBatch();
      }
      return currentBatch;
    }
Base class for VectorizedRowBatch data source.
Used in unit test only.
ql/src/test/org/apache/hadoop/hive/ql/exec/vector/util/FakeVectorRowBatchBase.java