public void init(VectorColumnMapping columnMapping) throws HiveException {
    init(
        columnMapping.getInputColumns(),
        columnMapping.getOutputColumns(),
        columnMapping.getTypeInfos());
  }
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