public void init(int startColumn) throws HiveException {

    final int count = sourceTypeInfos.length;
    allocateArrays(count);

    for (int i = 0; i < count; i++) {
      int outputColumn = startColumn + i;
      initTopLevelField(i, outputColumn, sourceTypeInfos[i]);
    }
  }
@param deserializeRead   Set useExternalBuffer to true to avoid buffer copying and to get
    more efficient reading.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorDeserializeRow.java