alamb commented on code in PR #10504:
URL: https://github.com/apache/datafusion/pull/10504#discussion_r1608069310
##########
datafusion/expr/src/udf.rs:
##########
@@ -426,6 +467,59 @@ pub trait ScalarUDFImpl: Debug + Send + Sync {
false
}
+ /// Computes the output interval for a [`ScalarUDFImpl`], given the input
+ /// intervals.
+ ///
+ /// # Parameters
+ ///
+ /// * `children` are the intervals for the children (inputs) of this
function.
+ ///
+ /// # Example
+ ///
+ /// If the function is `ABS(a)`, and the input interval is `a: [-3, 2]`,
+ /// then the output interval would be `[0, 3]`.
+ fn evaluate_bounds(&self, _input: &[&Interval]) -> Result<Interval> {
+ // We cannot assume the input datatype is the same of output type.
+ Interval::make_unbounded(&DataType::Null)
+ }
+
+ /// Updates bounds for child expressions, given a known interval for this
+ /// function. This is used to propagate constraints down through an
expression
+ /// tree.
+ ///
+ /// # Parameters
+ ///
+ /// * `interval` is the currently known interval for this function.
+ /// * `inputs` are the current intervals for the inputs (children) of this
function.
+ ///
+ /// # Returns
+ ///
+ /// A `Vec` of new intervals for the children, in order.
+ ///
+ /// If constraint propagation reveals an infeasibility for any child,
returns
+ /// [`None`]. If none of the children intervals change as a result of
+ /// propagation, may return an empty vector instead of cloning `children`.
+ /// This is the default (and conservative) return value.
+ ///
+ /// # Example
+ ///
+ /// If the function is `ABS(a)`, the current `interval` is `[4, 5]` and the
+ /// input `a` is given as `[-7, -6]`, then propagation would would return
+ /// `[-5, 5]`.
+ fn propagate_constraints(
+ &self,
+ _interval: &Interval,
+ _inputs: &[&Interval],
+ ) -> Result<Option<Vec<Interval>>> {
+ Ok(Some(vec![]))
+ }
+
+ /// Calculates the [`SortProperties`] of this function based on its
+ /// children's properties.
+ fn monotonicity(&self, _inputs: &[ExprProperties]) ->
Result<SortProperties> {
Review Comment:
Before we release this PR, I wonder if we should call this function
`sort_properties` or `calculate_sort`, rather than `monotonicty`
Calling it `monotonicty` may cause upgrade pain as the signature (types)
changed from
```rust
/// This function specifies monotonicity behaviors for User defined
scalar functions.
fn monotonicity(&self) -> Result<Option<FuncMonotonicity>> {
Ok(None)
}
```
It also seems like `monotonicity` doesn't accurately reflect what it does
any more, though I may misunderstand
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