fix: address review feedback on interval analysis for ScalarFunctionExpr

Author: davidlghellin

datafusion/expr/src/udf.rs

@@ -929,9 +929,9 @@ pub trait ScalarUDFImpl: Debug + DynEq + DynHash + Send + Sync + Any {
     fn propagate_constraints(
         &self,
         _interval: &Interval,
-        _inputs: &[&Interval],
+        inputs: &[&Interval],
     ) -> Result<Option<Vec<Interval>>> {
-        Ok(Some(vec![]))
+        Ok(Some(inputs.iter().map(|i| (*i).clone()).collect()))
     }
 
     /// Calculates the [`SortProperties`] of this function based on its children's properties.

datafusion/physical-expr/src/scalar_function.rs

@@ -302,7 +302,12 @@ impl PhysicalExpr for ScalarFunctionExpr {
     }
 
     fn evaluate_bounds(&self, children: &[&Interval]) -> Result<Interval> {
-        self.fun.evaluate_bounds(children)
+        let result = self.fun.evaluate_bounds(children)?;
+        if result.data_type() == DataType::Null {
+            Interval::make_unbounded(self.return_type())
+        } else {
+            Ok(result)
+        }
     }
 
     fn propagate_constraints(