Add dask-cudf workaround for missing rename_axis support in cudf

python/dask_cudf/dask_cudf/expr/_collection.py

@@ -15,6 +15,7 @@
 
 from dask import config
 from dask.dataframe.core import is_dataframe_like
+from dask.typing import no_default
 
 import cudf
 
@@ -90,6 +91,17 @@ def var(
             )
         )
 
+    def rename_axis(
+        self, mapper=no_default, index=no_default, columns=no_default, axis=0
+    ):
+        from dask_cudf.expr._expr import RenameAxisCudf
+
+        return new_collection(
+            RenameAxisCudf(
+                self, mapper=mapper, index=index, columns=columns, axis=axis
+            )
+        )
+
 
 class DataFrame(DXDataFrame, CudfFrameBase):
     @classmethod

python/dask_cudf/dask_cudf/expr/_expr.py

@@ -4,11 +4,12 @@
 import dask_expr._shuffle as _shuffle_module
 from dask_expr import new_collection
 from dask_expr._cumulative import CumulativeBlockwise
-from dask_expr._expr import Elemwise, Expr, VarColumns
+from dask_expr._expr import Elemwise, Expr, RenameAxis, VarColumns
 from dask_expr._reductions import Reduction, Var
 
 from dask.dataframe.core import is_dataframe_like, make_meta, meta_nonempty
 from dask.dataframe.dispatch import is_categorical_dtype
+from dask.typing import no_default
 
 import cudf
 
@@ -17,6 +18,19 @@
 ##
 
 
+class RenameAxisCudf(RenameAxis):
+    # TODO: Remove this after rename_axis is supported in cudf
+    # (See: https://github.com/rapidsai/cudf/issues/16895)
+    @staticmethod
+    def operation(df, index=no_default, **kwargs):
+        if index != no_default:
+            df.index.name = index
+            return df
+        raise NotImplementedError(
+            "Only `index` is supported for the cudf backend"
+        )
+
+
 class ToCudfBackend(Elemwise):
     # TODO: Inherit from ToBackend when rapids-dask-dependency
     # is pinned to dask>=2024.8.1

python/dask_cudf/dask_cudf/tests/test_core.py

@@ -1024,3 +1024,15 @@ def test_cov_corr(op, numeric_only):
     # (See: https://github.com/rapidsai/cudf/issues/12626)
     expect = getattr(df.to_pandas(), op)(numeric_only=numeric_only)
     dd.assert_eq(res, expect)
+
+
+def test_rename_axis_after_join():
+    df1 = cudf.DataFrame(index=["a", "b", "c"], data=dict(a=[1, 2, 3]))
+    df1.index.name = "test"
+    ddf1 = dd.from_pandas(df1, 2)
+
+    df2 = cudf.DataFrame(index=["a", "b", "d"], data=dict(b=[1, 2, 3]))
+    ddf2 = dd.from_pandas(df2, 2)
+    result = ddf1.join(ddf2, how="outer")
+    expected = df1.join(df2, how="outer")
+    dd.assert_eq(result, expected, check_index=False)