boolean ensureBatch() throws IOException {
    if (rowInBatch >= batch.size) {
      baseRow = super.getRowNumber();
      rowInBatch = 0;
      return super.nextBatch(batch);
    }
    return true;
  }
If the current batch is empty, get a new one.
@return true if we have rows available.
@throws IOException
ql/src/java/org/apache/hadoop/hive/ql/io/orc/RecordReaderImpl.java