fix: remove use of deprecated make_scalar_function

`make_scalar_function` has been deprecated since v36 [0].
It is being removed from the public api in v43 [1].

[0]: apache/datafusion#8878
[1]: apache/datafusion#12505

Author: Michael-J-Ward

src/udf.rs

@@ -24,39 +24,51 @@ use datafusion::arrow::datatypes::DataType;
 use datafusion::arrow::pyarrow::FromPyArrow;
 use datafusion::arrow::pyarrow::{PyArrowType, ToPyArrow};
 use datafusion::error::DataFusionError;
-use datafusion::logical_expr::create_udf;
 use datafusion::logical_expr::function::ScalarFunctionImplementation;
 use datafusion::logical_expr::ScalarUDF;
+use datafusion::logical_expr::{create_udf, ColumnarValue};
 
 use crate::expr::PyExpr;
 use crate::utils::parse_volatility;
 
+/// Create a Rust callable function fr a python function that expects pyarrow arrays
+fn pyarrow_function_to_rust(
+    func: PyObject,
+) -> impl Fn(&[ArrayRef]) -> Result<ArrayRef, DataFusionError> {
+    move |args: &[ArrayRef]| -> Result<ArrayRef, DataFusionError> {
+        Python::with_gil(|py| {
+            // 1. cast args to Pyarrow arrays
+            let py_args = args
+                .iter()
+                .map(|arg| arg.into_data().to_pyarrow(py).unwrap())
+                .collect::<Vec<_>>();
+            let py_args = PyTuple::new_bound(py, py_args);
+
+            // 2. call function
+            let value = func
+                .call_bound(py, py_args, None)
+                .map_err(|e| DataFusionError::Execution(format!("{e:?}")))?;
+
+            // 3. cast to arrow::array::Array
+            let array_data = ArrayData::from_pyarrow_bound(value.bind(py)).unwrap();
+            Ok(make_array(array_data))
+        })
+    }
+}
+
 /// Create a DataFusion's UDF implementation from a python function
 /// that expects pyarrow arrays. This is more efficient as it performs
 /// a zero-copy of the contents.
-fn to_rust_function(func: PyObject) -> ScalarFunctionImplementation {
-    #[allow(deprecated)]
-    datafusion::physical_plan::functions::make_scalar_function(
-        move |args: &[ArrayRef]| -> Result<ArrayRef, DataFusionError> {
-            Python::with_gil(|py| {
-                // 1. cast args to Pyarrow arrays
-                let py_args = args
-                    .iter()
-                    .map(|arg| arg.into_data().to_pyarrow(py).unwrap())
-                    .collect::<Vec<_>>();
-                let py_args = PyTuple::new_bound(py, py_args);
-
-                // 2. call function
-                let value = func
-                    .call_bound(py, py_args, None)
-                    .map_err(|e| DataFusionError::Execution(format!("{e:?}")))?;
+fn to_scalar_function_impl(func: PyObject) -> ScalarFunctionImplementation {
+    // Make the python function callable from rust
+    let pyarrow_func = pyarrow_function_to_rust(func);
 
-                // 3. cast to arrow::array::Array
-                let array_data = ArrayData::from_pyarrow_bound(value.bind(py)).unwrap();
-                Ok(make_array(array_data))
-            })
-        },
-    )
+    // Convert input/output from datafusion ColumnarValue to arrow arrays
+    Arc::new(move |args: &[ColumnarValue]| {
+        let array_refs = ColumnarValue::values_to_arrays(args)?;
+        let array_result = pyarrow_func(&array_refs)?;
+        Ok(array_result.into())
+    })
 }
 
 /// Represents a PyScalarUDF
@@ -82,7 +94,7 @@ impl PyScalarUDF {
             input_types.0,
             Arc::new(return_type.0),
             parse_volatility(volatility)?,
-            to_rust_function(func),
+            to_scalar_function_impl(func),
         );
         Ok(Self { function })
     }