alamb opened a new issue, #9879: URL: https://github.com/apache/datafusion/issues/9879
### Is your feature request related to a problem or challenge? While reviewing https://github.com/apache/arrow-datafusion/pull/9869 from @tinfoil-knight I was confused about the [`ScalarUDFImpl::monotonicity`](https://docs.rs/datafusion/latest/datafusion/logical_expr/trait.ScalarUDFImpl.html#method.monotonicity) API ```rust // This function specifies monotonicity behaviors for User defined scalar functions. fn monotonicity(&self) -> Result<Option<Vec<Option<bool>>>, DataFusionError> {..} ``` The challenge is the cognative complexity of understanding what `Result<Option<Vec<Option<bool>>>` means The actual code is defined in terms `FuncMonotonicity` https://github.com/apache/arrow-datafusion/blob/57c0bc65280c467ef6f5a498c6e78a616401b286/datafusion/expr/src/signature.rs#L350-L356 However, since it is a typedef it doesn't show up in the Rust docs ### Describe the solution you'd like An easy to understand Monotonicity API ### Describe alternatives you've considered I think it would be great to have an API like this: ```rust // This function specifies monotonicity behaviors for User defined scalar functions. fn monotonicity(&self) -> Result<Monotonicity>, DataFusionError> {..} ``` And then we could make `Monotonicity` an enum that captured the relevant data. This would both be easier to understand and likely more efficient as well Something like ```rust /// Monotonicity of a function with respect to its arguments. /// /// A function is [monotonic] if it preserves the relative order of its inputs. /// /// [monotonic]: https://en.wikipedia.org/wiki/Monotonic_function pub enum Monotonicity { /// not monotonic or unknown monotonicity None, /// Increasing with respect to all of its arguments Increasing, /// Decreasing with respect to all of its arguments Decreasing, /// Each element of this vector corresponds to an argument and indicates whether /// the function's behavior is monotonic, or non-monotonic/unknown for that argument, namely: /// - `None` signifies unknown monotonicity or non-monotonicity. /// - `Some(true)` indicates that the function is monotonically increasing w.r.t. the argument in question. /// - Some(false) indicates that the function is monotonically decreasing w.r.t. the argument in question. Mixed(Vec<bool>), } ``` I think this would be much eaiser to reason about ### Additional context _No response_ -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
