Correct nullability flag

Author: timsaucer

datafusion/expr/src/udwf.rs

@@ -280,7 +280,7 @@ where
 ///        unimplemented!()
 ///    }
 ///    fn field(&self, field_args: WindowUDFFieldArgs) -> Result<Field> {
-///      if let Some(DataType::Int32) = field_args.get_input_type(0) {
+///      if let Some(DataType::Int32) = field_args.get_input_field(0).map(|f| f.data_type().clone()) {
 ///        Ok(Field::new(field_args.name(), DataType::Int32, false))
 ///      } else {
 ///        plan_err!("smooth_it only accepts Int32 arguments")

datafusion/functions-window/src/lead_lag.rs

@@ -303,11 +303,11 @@ fn parse_expr_type(input_fields: &[Field]) -> Result<Field> {
 
     // Handles the most common case where NULL is unexpected
     if !expr_field.data_type().is_null() {
-        return Ok(expr_field.clone());
+        return Ok(expr_field.clone().with_nullable(true));
     }
 
     let default_value_field = input_fields.get(2).unwrap_or(&null_field);
-    Ok(default_value_field.clone())
+    Ok(default_value_field.clone().with_nullable(true))
 }
 
 /// Handles type coercion and null value refinement for default value

datafusion/functions-window/src/macros.rs

@@ -286,7 +286,7 @@ macro_rules! get_or_init_udwf {
 /// #     fn field(&self, field_args: WindowUDFFieldArgs) -> datafusion_common::Result<Field> {
 /// #         Ok(Field::new(
 /// #             field_args.name(),
-/// #             field_args.get_input_type(0).unwrap(),
+/// #             field_args.get_input_field(0).unwrap().data_type().clone(),
 /// #             false,
 /// #         ))
 /// #     }
@@ -557,7 +557,7 @@ macro_rules! create_udwf_expr {
 /// #     fn field(&self, field_args: WindowUDFFieldArgs) -> datafusion_common::Result<Field> {
 /// #         Ok(Field::new(
 /// #             field_args.name(),
-/// #             field_args.get_input_type(0).unwrap(),
+/// #             field_args.get_input_field(0).unwrap().data_type().clone(),
 /// #             false,
 /// #         ))
 /// #     }
@@ -646,7 +646,7 @@ macro_rules! create_udwf_expr {
 /// #     fn field(&self, field_args: WindowUDFFieldArgs) -> datafusion_common::Result<Field> {
 /// #         Ok(Field::new(
 /// #             field_args.name(),
-/// #             field_args.get_input_type(0).unwrap(),
+/// #             field_args.get_input_field(0).unwrap().data_type().clone(),
 /// #             false,
 /// #         ))
 /// #     }

datafusion/functions-window/src/nth_value.rs

@@ -270,13 +270,14 @@ impl WindowUDFImpl for NthValue {
     }
 
     fn field(&self, field_args: WindowUDFFieldArgs) -> Result<Field> {
-        let return_field = field_args
+        let return_type = field_args
             .input_fields()
             .first()
+            .map(|f| f.data_type())
             .cloned()
-            .unwrap_or(Field::new("f", DataType::Null, true));
+            .unwrap_or(DataType::Null);
 
-        Ok(return_field.with_name(field_args.name()))
+        Ok(Field::new(field_args.name(), return_type, true))
     }
 
     fn reverse_expr(&self) -> ReversedUDWF {