@Override
      public Object setValue(Object struct, ColumnVector column, int row) throws HiveException {
        if (struct == null) {
          struct = initValue(null);
        }

        return setValueInternal(struct, column, row);
      }
Compiles the appropriate vector expression writers based on a struct object
inspector.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorExpressionWriterFactory.java