static TimestampWritableV2 nextTimestamp(ColumnVector vector,
                                           int row,
                                           Object previous) {
    if (vector.isRepeating) {
      row = 0;
    }
    if (vector.noNulls || !vector.isNull[row]) {
      TimestampWritableV2 result;
      if (previous == null || previous.getClass() != TimestampWritableV2.class) {
        result = new TimestampWritableV2();
      } else {
        result = (TimestampWritableV2) previous;
      }
      TimestampColumnVector tcv = (TimestampColumnVector) vector;
      result.setInternal(tcv.time[row], tcv.nanos[row]);
      return result;
    } else {
      return null;
    }
  }
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