@Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("VectorCopyRow ");
    for (CopyRow copyRow : subRowToBatchCopiersByValue) {
      if (sb.length() > 0) {
        sb.append(", ");
      }
      sb.append(copyRow.getClass().getName());
      sb.append(" inColumnIndex " + copyRow.inColumnIndex);
      sb.append(" outColumnIndex " + copyRow.outColumnIndex);
    }
    return sb.toString();
  }
This class copies specified columns of a row from one VectorizedRowBatch to another.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorCopyRow.java