public void init(List<String> typeNames) throws HiveException {

    final int count = typeNames.size();
    allocateArrays(count);

    for (int i = 0; i < count; i++) {

      final TypeInfo typeInfo =
          TypeInfoUtils.getTypeInfoFromTypeString(typeNames.get(i));

      initTargetEntry(i, i, typeInfo);
    }
  }
This class assigns specified columns of a row from a Writable row objects.

The caller provides the data types and projection column numbers of a subset of the columns
to assign.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorAssignRow.java