done

lib/python3.11/site-packages/narwhals/_sql/dataframe.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, Protocol
+
+from narwhals._compliant.dataframe import CompliantLazyFrame
+from narwhals._compliant.typing import (
+    CompliantExprT_contra,
+    NativeExprT,
+    NativeLazyFrameT,
+)
+from narwhals._translate import ToNarwhalsT_co
+from narwhals._utils import check_columns_exist
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+
+    from typing_extensions import Self, TypeAlias
+
+    from narwhals._compliant.window import WindowInputs
+    from narwhals._sql.expr import SQLExpr
+    from narwhals.exceptions import ColumnNotFoundError
+
+    Incomplete: TypeAlias = Any
+
+
+class SQLLazyFrame(
+    CompliantLazyFrame[CompliantExprT_contra, NativeLazyFrameT, ToNarwhalsT_co],
+    Protocol[CompliantExprT_contra, NativeLazyFrameT, ToNarwhalsT_co],
+):
+    def _evaluate_window_expr(
+        self,
+        expr: SQLExpr[Self, NativeExprT],
+        /,
+        window_inputs: WindowInputs[NativeExprT],
+    ) -> NativeExprT:
+        result = expr.window_function(self, window_inputs)
+        assert len(result) == 1  # debug assertion  # noqa: S101
+        return result[0]
+
+    def _evaluate_expr(self, expr: CompliantExprT_contra, /) -> Any:
+        result = expr(self)
+        assert len(result) == 1  # debug assertion  # noqa: S101
+        return result[0]
+
+    def _check_columns_exist(self, subset: Sequence[str]) -> ColumnNotFoundError | None:
+        return check_columns_exist(subset, available=self.columns)