It should use the helpers since the output size is known. **Reporter**: [Francois Saint-Jacques](https://issues.apache.org/jira/browse/ARROW-6123) / @fsaintjacques #### Related issues: - [[C++] C++ array kernels framework and execution buildout (umbrella issue)](https://github.com/apache/arrow/issues/25028) (is a child of) <sub>**Note**: *This issue was originally created as [ARROW-6123](https://issues.apache.org/jira/browse/ARROW-6123). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*</sub>