Remove BuiltInWindowFunction

datafusion/expr/src/expr.rs

@@ -27,10 +27,7 @@ use crate::expr_fn::binary_expr;
 use crate::logical_plan::Subquery;
 use crate::utils::expr_to_columns;
 use crate::Volatility;
-use crate::{
-    udaf, BuiltInWindowFunction, ExprSchemable, Operator, Signature, WindowFrame,
-    WindowUDF,
-};
+use crate::{udaf, ExprSchemable, Operator, Signature, WindowFrame, WindowUDF};
 
 use arrow::datatypes::{DataType, FieldRef};
 use datafusion_common::cse::HashNode;
@@ -697,13 +694,13 @@ impl AggregateFunction {
     }
 }
 
-/// WindowFunction
+/// A function used as a SQL window function
+///
+/// In SQL, you can use:
+/// - Actual window functions ([`WindowUDF`])
+/// - Noraml aggregate functions ([`AggregateUDF`])
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Hash)]
-/// Defines which implementation of an aggregate function DataFusion should call.
 pub enum WindowFunctionDefinition {
-    /// A built in aggregate function that leverages an aggregate function
-    /// A a built-in window function
-    BuiltInWindowFunction(BuiltInWindowFunction),
     /// A user defined aggregate function
     AggregateUDF(Arc<crate::AggregateUDF>),
     /// A user defined aggregate function
@@ -719,9 +716,6 @@ impl WindowFunctionDefinition {
         display_name: &str,
     ) -> Result<DataType> {
         match self {
-            WindowFunctionDefinition::BuiltInWindowFunction(fun) => {
-                fun.return_type(input_expr_types)
-            }
             WindowFunctionDefinition::AggregateUDF(fun) => {
                 fun.return_type(input_expr_types)
             }
@@ -734,7 +728,6 @@ impl WindowFunctionDefinition {
     /// The signatures supported by the function `fun`.
     pub fn signature(&self) -> Signature {
         match self {
-            WindowFunctionDefinition::BuiltInWindowFunction(fun) => fun.signature(),
             WindowFunctionDefinition::AggregateUDF(fun) => fun.signature().clone(),
             WindowFunctionDefinition::WindowUDF(fun) => fun.signature().clone(),
         }
@@ -743,7 +736,6 @@ impl WindowFunctionDefinition {
     /// Function's name for display
     pub fn name(&self) -> &str {
         match self {
-            WindowFunctionDefinition::BuiltInWindowFunction(fun) => fun.name(),
             WindowFunctionDefinition::WindowUDF(fun) => fun.name(),
             WindowFunctionDefinition::AggregateUDF(fun) => fun.name(),
         }
@@ -753,19 +745,12 @@ impl WindowFunctionDefinition {
 impl Display for WindowFunctionDefinition {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
-            WindowFunctionDefinition::BuiltInWindowFunction(fun) => Display::fmt(fun, f),
             WindowFunctionDefinition::AggregateUDF(fun) => Display::fmt(fun, f),
             WindowFunctionDefinition::WindowUDF(fun) => Display::fmt(fun, f),
         }
     }
 }
 
-impl From<BuiltInWindowFunction> for WindowFunctionDefinition {
-    fn from(value: BuiltInWindowFunction) -> Self {
-        Self::BuiltInWindowFunction(value)
-    }
-}
-
 impl From<Arc<crate::AggregateUDF>> for WindowFunctionDefinition {
     fn from(value: Arc<crate::AggregateUDF>) -> Self {
         Self::AggregateUDF(value)

datafusion/expr/src/expr_schema.rs

@@ -481,12 +481,6 @@ impl Expr {
             .map(|e| e.get_type(schema))
             .collect::<Result<Vec<_>>>()?;
         match fun {
-            WindowFunctionDefinition::BuiltInWindowFunction(window_fun) => {
-                let return_type = window_fun.return_type(&data_types)?;
-                let nullable =
-                    !["RANK", "NTILE", "CUME_DIST"].contains(&window_fun.name());
-                Ok((return_type, nullable))
-            }
             WindowFunctionDefinition::AggregateUDF(udaf) => {
                 let new_types = data_types_with_aggregate_udf(&data_types, udaf)
                     .map_err(|err| {

datafusion/expr/src/lib.rs

@@ -28,7 +28,6 @@
 //!
 //! The [expr_fn] module contains functions for creating expressions.
 
-mod built_in_window_function;
 mod literal;
 mod operation;
 mod partition_evaluator;
@@ -67,7 +66,6 @@ pub mod var_provider;
 pub mod window_frame;
 pub mod window_state;
 
-pub use built_in_window_function::BuiltInWindowFunction;
 pub use datafusion_expr_common::accumulator::Accumulator;
 pub use datafusion_expr_common::columnar_value::ColumnarValue;
 pub use datafusion_expr_common::groups_accumulator::{EmitTo, GroupsAccumulator};

datafusion/expr/src/udwf.rs

@@ -39,8 +39,16 @@ use datafusion_functions_window_common::field::WindowUDFFieldArgs;
 use datafusion_functions_window_common::partition::PartitionEvaluatorArgs;
 use datafusion_physical_expr_common::physical_expr::PhysicalExpr;
 
-/// Logical representation of a user-defined window function (UDWF)
-/// A UDWF is different from a UDF in that it is stateful across batches.
+/// Logical representation of a user-defined window function (UDWF).
+///
+/// A Window Function is called via the SQL `OVER` clause:
+///
+/// ```sql
+/// SELECT first_value(col) OVER (PARTITION BY a, b ORDER BY c) FROM foo;
+/// ```
+///
+/// A UDWF is different from a user defined function (UDF) in that it is
+/// stateful across batches.
 ///
 /// See the documentation on [`PartitionEvaluator`] for more details
 ///

datafusion/physical-plan/src/windows/mod.rs

@@ -103,9 +103,6 @@ pub fn create_window_expr(
     ignore_nulls: bool,
 ) -> Result<Arc<dyn WindowExpr>> {
     Ok(match fun {
-        WindowFunctionDefinition::BuiltInWindowFunction(_fun) => {
-            unreachable!()
-        }
         WindowFunctionDefinition::AggregateUDF(fun) => {
             let aggregate = AggregateExprBuilder::new(Arc::clone(fun), args.to_vec())
                 .schema(Arc::new(input_schema.clone()))
@@ -120,7 +117,6 @@ pub fn create_window_expr(
                 aggregate,
             )
         }
-        // TODO: Ordering not supported for Window UDFs yet
         WindowFunctionDefinition::WindowUDF(fun) => Arc::new(BuiltInWindowExpr::new(
             create_udwf_window_expr(fun, args, input_schema, name, ignore_nulls)?,
             partition_by,

datafusion/proto/proto/datafusion.proto

@@ -507,24 +507,9 @@ message ScalarUDFExprNode {
   optional bytes fun_definition = 3;
 }
 
-enum BuiltInWindowFunction {
-  UNSPECIFIED = 0; // https://protobuf.dev/programming-guides/dos-donts/#unspecified-enum
-  // ROW_NUMBER = 0;
-  //  RANK = 1;
-  //  DENSE_RANK = 2;
-  //  PERCENT_RANK = 3;
-  //  CUME_DIST = 4;
-  //  NTILE = 5;
-  // LAG = 6;
-  // LEAD = 7;
-  // FIRST_VALUE = 8;
-  // LAST_VALUE = 9;
-  // NTH_VALUE = 10;
-}
-
 message WindowExprNode {
   oneof window_function {
-    BuiltInWindowFunction built_in_function = 2;
+    // BuiltInWindowFunction built_in_function = 2;
     string udaf = 3;
     string udwf = 9;
   }
@@ -866,7 +851,7 @@ message PhysicalAggregateExprNode {
 
 message PhysicalWindowExprNode {
   oneof window_function {
-    BuiltInWindowFunction built_in_function = 2;
+    // BuiltInWindowFunction built_in_function = 2;
     string user_defined_aggr_function = 3;
   }
   repeated PhysicalExprNode args = 4;