Rename Window to WindowExpr so we can define Window to mean a window …

…definition to be reused

python/datafusion/expr.py

@@ -92,7 +92,7 @@
 Union = expr_internal.Union
 Unnest = expr_internal.Unnest
 UnnestExpr = expr_internal.UnnestExpr
-Window = expr_internal.Window
+WindowExpr = expr_internal.WindowExpr
 
 __all__ = [
     "Expr",
@@ -154,6 +154,7 @@
     "Partitioning",
     "Repartition",
     "Window",
+    "WindowExpr",
     "WindowFrame",
     "WindowFrameBound",
 ]
@@ -542,32 +543,25 @@ def window_frame(self, window_frame: WindowFrame) -> ExprFuncBuilder:
         """
         return ExprFuncBuilder(self.expr.window_frame(window_frame.window_frame))
 
-    def over(
-        self,
-        partition_by: Optional[list[Expr]] = None,
-        window_frame: Optional[WindowFrame] = None,
-        order_by: Optional[list[SortExpr | Expr]] = None,
-        null_treatment: Optional[NullTreatment] = None,
-    ) -> Expr:
+    def over(self, window: Window) -> Expr:
         """Turn an aggregate function into a window function.
 
         This function turns any aggregate function into a window function. With the
         exception of ``partition_by``, how each of the parameters is used is determined
         by the underlying aggregate function.
 
         Args:
-            partition_by: Expressions to partition the window frame on
-            window_frame: Specify the window frame parameters
-            order_by: Set ordering within the window frame
-            null_treatment: Set how to handle null values
+            window: Window definition
         """
-        partition_by_raw = expr_list_to_raw_expr_list(partition_by)
-        order_by_raw = sort_list_to_raw_sort_list(order_by)
+        partition_by_raw = expr_list_to_raw_expr_list(window._partition_by)
+        order_by_raw = sort_list_to_raw_sort_list(window._order_by)
         window_frame_raw = (
-            window_frame.window_frame if window_frame is not None else None
+            window._window_frame.window_frame
+            if window._window_frame is not None
+            else None
         )
         null_treatment_raw = (
-            null_treatment.value if null_treatment is not None else None
+            window._null_treatment.value if window._null_treatment is not None else None
         )
 
         return Expr(
@@ -621,6 +615,30 @@ def build(self) -> Expr:
         return Expr(self.builder.build())
 
 
+class Window:
+    """Define reusable window parameters."""
+
+    def __init__(
+        self,
+        partition_by: Optional[list[Expr]] = None,
+        window_frame: Optional[WindowFrame] = None,
+        order_by: Optional[list[SortExpr | Expr]] = None,
+        null_treatment: Optional[NullTreatment] = None,
+    ) -> None:
+        """Construct a window definition.
+
+        Args:
+            partition_by: Partitions for window operation
+            window_frame: Define the start and end bounds of the window frame
+            order_by: Set ordering
+            null_treatment: Indicate how nulls are to be treated
+        """
+        self._partition_by = partition_by
+        self._window_frame = window_frame
+        self._order_by = order_by
+        self._null_treatment = null_treatment
+
+
 class WindowFrame:
     """Defines a window frame for performing window operations."""
 

python/datafusion/tests/test_dataframe.py

@@ -31,6 +31,7 @@
     literal,
     udf,
 )
+from datafusion.expr import Window
 
 
 @pytest.fixture
@@ -389,27 +390,29 @@ def test_distinct():
     (
         "first_value",
         f.first_value(column("a")).over(
-            partition_by=[column("c")], order_by=[column("b")]
+            Window(partition_by=[column("c")], order_by=[column("b")])
         ),
         [1, 1, 1, 1, 5, 5, 5],
     ),
     (
         "last_value",
         f.last_value(column("a")).over(
-            partition_by=[column("c")],
-            order_by=[column("b")],
-            window_frame=WindowFrame("rows", None, None),
+            Window(
+                partition_by=[column("c")],
+                order_by=[column("b")],
+                window_frame=WindowFrame("rows", None, None),
+            )
         ),
         [3, 3, 3, 3, 6, 6, 6],
     ),
     (
         "3rd_value",
-        f.nth_value(column("b"), 3).over(order_by=[column("a")]),
+        f.nth_value(column("b"), 3).over(Window(order_by=[column("a")])),
         [None, None, 7, 7, 7, 7, 7],
     ),
     (
         "avg",
-        f.round(f.avg(column("b")).over(order_by=[column("a")]), literal(3)),
+        f.round(f.avg(column("b")).over(Window(order_by=[column("a")])), literal(3)),
         [7.0, 7.0, 7.0, 7.333, 7.75, 7.75, 8.0],
     ),
 ]

src/expr.rs

@@ -791,7 +791,7 @@ pub(crate) fn init_module(m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_class::<drop_table::PyDropTable>()?;
     m.add_class::<repartition::PyPartitioning>()?;
     m.add_class::<repartition::PyRepartition>()?;
-    m.add_class::<window::PyWindow>()?;
+    m.add_class::<window::PyWindowExpr>()?;
     m.add_class::<window::PyWindowFrame>()?;
     m.add_class::<window::PyWindowFrameBound>()?;
     Ok(())

src/expr/window.rs

@@ -32,9 +32,9 @@ use super::py_expr_list;
 
 use crate::errors::py_datafusion_err;
 
-#[pyclass(name = "Window", module = "datafusion.expr", subclass)]
+#[pyclass(name = "WindowExpr", module = "datafusion.expr", subclass)]
 #[derive(Clone)]
-pub struct PyWindow {
+pub struct PyWindowExpr {
     window: Window,
 }
 
@@ -62,15 +62,15 @@ pub struct PyWindowFrameBound {
     frame_bound: WindowFrameBound,
 }
 
-impl From<PyWindow> for Window {
-    fn from(window: PyWindow) -> Window {
+impl From<PyWindowExpr> for Window {
+    fn from(window: PyWindowExpr) -> Window {
         window.window
     }
 }
 
-impl From<Window> for PyWindow {
-    fn from(window: Window) -> PyWindow {
-        PyWindow { window }
+impl From<Window> for PyWindowExpr {
+    fn from(window: Window) -> PyWindowExpr {
+        PyWindowExpr { window }
     }
 }
 
@@ -80,7 +80,7 @@ impl From<WindowFrameBound> for PyWindowFrameBound {
     }
 }
 
-impl Display for PyWindow {
+impl Display for PyWindowExpr {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(
             f,
@@ -103,7 +103,7 @@ impl Display for PyWindowFrame {
 }
 
 #[pymethods]
-impl PyWindow {
+impl PyWindowExpr {
     /// Returns the schema of the Window
     pub fn schema(&self) -> PyResult<PyDFSchema> {
         Ok(self.window.schema.as_ref().clone().into())
@@ -283,7 +283,7 @@ impl PyWindowFrameBound {
     }
 }
 
-impl LogicalNode for PyWindow {
+impl LogicalNode for PyWindowExpr {
     fn inputs(&self) -> Vec<PyLogicalPlan> {
         vec![self.window.input.as_ref().clone().into()]
     }

src/functions.rs

@@ -15,8 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use std::ptr::null;
-
 use datafusion::functions_aggregate::all_default_aggregate_functions;
 use datafusion::logical_expr::window_function;
 use datafusion::logical_expr::ExprFunctionExt;

src/sql/logical.rs

@@ -34,7 +34,7 @@ use crate::expr::subquery::PySubquery;
 use crate::expr::subquery_alias::PySubqueryAlias;
 use crate::expr::table_scan::PyTableScan;
 use crate::expr::unnest::PyUnnest;
-use crate::expr::window::PyWindow;
+use crate::expr::window::PyWindowExpr;
 use datafusion::logical_expr::LogicalPlan;
 use pyo3::prelude::*;
 
@@ -80,7 +80,7 @@ impl PyLogicalPlan {
             LogicalPlan::Subquery(plan) => PySubquery::from(plan.clone()).to_variant(py),
             LogicalPlan::SubqueryAlias(plan) => PySubqueryAlias::from(plan.clone()).to_variant(py),
             LogicalPlan::Unnest(plan) => PyUnnest::from(plan.clone()).to_variant(py),
-            LogicalPlan::Window(plan) => PyWindow::from(plan.clone()).to_variant(py),
+            LogicalPlan::Window(plan) => PyWindowExpr::from(plan.clone()).to_variant(py),
             LogicalPlan::Repartition(_)
             | LogicalPlan::Union(_)
             | LogicalPlan::Statement(_)