@Override
  public void reset() {
    reset(cols);
  }
Resets the row batch to default state
 - sets selectedInUse to false
 - sets size to 0
 - sets endOfFile to false
 - resets each column
 - inits each column
storage-api/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorizedRowBatch.java