Rewrites column.__setitem__, Use boolean_mask_scatter

python/cudf/cudf/_lib/copying.pyx

@@ -1,4 +1,4 @@
-# Copyright (c) 2020-2021, NVIDIA CORPORATION.
+# Copyright (c) 2020-2022, NVIDIA CORPORATION.
 
 import pickle
 
@@ -537,11 +537,11 @@ def copy_if_else(object lhs, object rhs, Column boolean_mask):
                 as_device_scalar(lhs), as_device_scalar(rhs), boolean_mask)
 
 
-def _boolean_mask_scatter_table(input_table, target_table,
-                                Column boolean_mask):
+def _boolean_mask_scatter_columns(list input_columns, list target_columns,
+                                  Column boolean_mask):
 
-    cdef table_view input_table_view = table_view_from_columns(input_table)
-    cdef table_view target_table_view = table_view_from_columns(target_table)
+    cdef table_view input_table_view = table_view_from_columns(input_columns)
+    cdef table_view target_table_view = table_view_from_columns(target_columns)
     cdef column_view boolean_mask_view = boolean_mask.view()
 
     cdef unique_ptr[table] c_result
@@ -555,14 +555,10 @@ def _boolean_mask_scatter_table(input_table, target_table,
             )
         )
 
-    return data_from_unique_ptr(
-        move(c_result),
-        column_names=target_table._column_names,
-        index_names=target_table._index._column_names
-    )
+    return columns_from_unique_ptr(move(c_result))
 
 
-def _boolean_mask_scatter_scalar(list input_scalars, target_table,
+def _boolean_mask_scatter_scalar(list input_scalars, list target_columns,
                                  Column boolean_mask):
 
     cdef vector[reference_wrapper[constscalar]] input_scalar_vector
@@ -571,7 +567,7 @@ def _boolean_mask_scatter_scalar(list input_scalars, target_table,
     for scl in input_scalars:
         input_scalar_vector.push_back(reference_wrapper[constscalar](
             scl.get_raw_ptr()[0]))
-    cdef table_view target_table_view = table_view_from_columns(target_table)
+    cdef table_view target_table_view = table_view_from_columns(target_columns)
     cdef column_view boolean_mask_view = boolean_mask.view()
 
     cdef unique_ptr[table] c_result
@@ -585,29 +581,37 @@ def _boolean_mask_scatter_scalar(list input_scalars, target_table,
             )
         )
 
-    return data_from_unique_ptr(
-        move(c_result),
-        column_names=target_table._column_names,
-        index_names=target_table._index._column_names
-    )
+    return columns_from_unique_ptr(move(c_result))
 
 
-# TODO: This function is currently unused but should be used in
-# ColumnBase.__setitem__, see https://github.com/rapidsai/cudf/issues/8667.
-def boolean_mask_scatter(object input, target_table,
+def boolean_mask_scatter(list input_, list target_columns,
                          Column boolean_mask):
+    """Copy the target columns, replacing masked rows with input data.
+
+    The ``input_`` data can be a list of columns or as a list of scalars.
+    A list of input columns will be used to replace corresponding rows in the
+    target columns for which the boolean mask is ``True``. For the nth ``True``
+    in the boolean mask, the nth row in ``input_`` is used to replace. A list
+    of input scalars will replace all rows in the target columns for which the
+    boolean mask is ``True``.
+    """
+    if len(input_) != len(target_columns):
+        raise ValueError("Mismatched number of input and target columns.")
+
+    if len(input_) == 0:
+        return []
 
-    if isinstance(input, cudf.core.frame.Frame):
-        return _boolean_mask_scatter_table(
-            input,
-            target_table,
+    if isinstance(input_[0], Column):
+        return _boolean_mask_scatter_columns(
+            input_,
+            target_columns,
             boolean_mask
         )
     else:
-        scalar_list = [as_device_scalar(i) for i in input]
+        scalar_list = [as_device_scalar(i) for i in input_]
         return _boolean_mask_scatter_scalar(
             scalar_list,
-            target_table,
+            target_columns,
             boolean_mask
         )
 

python/cudf/cudf/core/column/column.py

@@ -80,6 +80,9 @@
 from cudf.utils.utils import NotIterable, mask_dtype
 
 T = TypeVar("T", bound="ColumnBase")
+# TODO: This workaround allows type hints for `slice`, since `slice` is a
+# method in ColumnBase.
+Slice = TypeVar("Slice", bound=slice)
 
 
 class ColumnBase(Column, Serializable, NotIterable):
@@ -315,22 +318,24 @@ def _fill(
         if end <= begin or begin >= self.size:
             return self if inplace else self.copy()
 
-        fill_scalar = as_device_scalar(fill_value, self.dtype)
+        # Constructing a cuDF scalar can cut unnecessary DtoH copy if
+        # the scalar is None when calling `is_valid`.
+        slr = cudf.Scalar(fill_value, dtype=self.dtype)
 
         if not inplace:
-            return libcudf.filling.fill(self, begin, end, fill_scalar)
+            return libcudf.filling.fill(self, begin, end, slr.device_value)
 
         if is_string_dtype(self.dtype):
             return self._mimic_inplace(
-                libcudf.filling.fill(self, begin, end, fill_scalar),
+                libcudf.filling.fill(self, begin, end, slr.device_value),
                 inplace=True,
             )
 
-        if fill_value is None and not self.nullable:
+        if not slr.is_valid() and not self.nullable:
             mask = create_null_mask(self.size, state=MaskState.ALL_VALID)
             self.set_base_mask(mask)
 
-        libcudf.filling.fill_in_place(self, begin, end, fill_scalar)
+        libcudf.filling.fill_in_place(self, begin, end, slr.device_value)
 
         return self
 
@@ -481,82 +486,121 @@ def __getitem__(self, arg) -> Union[ScalarLike, ColumnBase]:
 
     def __setitem__(self, key: Any, value: Any):
         """
-        Set the value of self[key] to value.
+        Set the value of ``self[key]`` to ``value``.
 
-        If value and self are of different types,
-        value is coerced to self.dtype
+        If ``value`` and ``self`` are of different types, ``value`` is coerced
+        to ``self.dtype``. Assumes ``self`` and ``value`` are index-aligned.
         """
 
+        # Normalize value to scalar/column
+        value_normalized = (
+            cudf.Scalar(value, dtype=self.dtype)
+            if is_scalar(value)
+            else as_column(value, dtype=self.dtype)
+        )
+
+        out: Optional[ColumnBase]  # If None, no need to perform mimic inplace.
         if isinstance(key, slice):
-            key_start, key_stop, key_stride = key.indices(len(self))
-            if key_start < 0:
-                key_start = key_start + len(self)
-            if key_stop < 0:
-                key_stop = key_stop + len(self)
-            if key_start >= key_stop:
-                return self.copy()
-            if (key_stride is None or key_stride == 1) and is_scalar(value):
-                return self._fill(value, key_start, key_stop, inplace=True)
-            if key_stride != 1 or key_stride is not None or is_scalar(value):
-                key = arange(
-                    start=key_start,
-                    stop=key_stop,
-                    step=key_stride,
-                    dtype=cudf.dtype(np.int32),
-                )
-                nelem = len(key)
-            else:
-                nelem = abs(key_stop - key_start)
+            out = self._scatter_by_slice(key, value_normalized)
         else:
             key = as_column(key)
+            if not isinstance(key, cudf.core.column.NumericalColumn):
+                raise ValueError(f"Invalid scatter map type {key.dtype}.")
+            out = self._scatter_by_column(key, value_normalized)
+
+        if out:
+            self._mimic_inplace(out, inplace=True)
+
+    def _scatter_by_slice(
+        self, key: Slice, value: Union[cudf.core.scalar.Scalar, ColumnBase]
+    ) -> Optional[ColumnBase]:
+        """If this function returns None, it's either a no-op (slice is empty),
+        or the inplace replacement is already performed (fill-in-place).
+        """
+        nelem: int  # the number of elements to scatter
+
+        start, stop, step = key.indices(len(self))
+        if start >= stop:
+            return None
+        nelem = (stop - start) // step
+
+        self._check_scatter_key_length(nelem, value)
+
+        if step == 1:
+            if isinstance(value, cudf.core.scalar.Scalar):
+                return self._fill(value, start, stop, inplace=True)
+            else:
+                return libcudf.copying.copy_range(
+                    value, self, 0, nelem, start, stop, False
+                )
+
+        # step != 1, create a scatter map with arange
+        scatter_map = arange(
+            start=start, stop=stop, step=step, dtype=cudf.dtype(np.int32),
+        )
+
+        return self._scatter_by_column(scatter_map, value)
+
+    def _scatter_by_column(
+        self,
+        key: "cudf.core.column.NumericalColumn",
+        value: Union[cudf.core.scalar.Scalar, ColumnBase],
+    ) -> ColumnBase:
+        nelem = len(key)  # the number of elements to scatter
+
+        if is_bool_dtype(key.dtype):
+            if len(key) != len(self):
+                raise ValueError(
+                    "Boolean mask must be of same length as column"
+                )
+            skip_reducing_key = False
+            if isinstance(value, ColumnBase):
+                if len(self) == len(value):
+                    # Both value and key are aligned to self. Thus, the values
+                    # corresponding to the false values in key should be
+                    # ignored.
+                    value = value.apply_boolean_mask(key)
+                    # After applying boolean mask, the length of value equals
+                    # the number of elements to scatter, we can skip computing
+                    # the sum of ``key`` below.
+                    nelem = len(value)
+                    skip_reducing_key = True
+            # Compute the number of element to scatter by summing all `True`s
+            # in the boolean mask.
+            nelem = key.sum() if not skip_reducing_key else nelem
+
+        self._check_scatter_key_length(nelem, value)
+
+        try:
             if is_bool_dtype(key.dtype):
-                if not len(key) == len(self):
-                    raise ValueError(
-                        "Boolean mask must be of same length as column"
-                    )
-                key = arange(len(self))[key]
-                if hasattr(value, "__len__") and len(value) == len(self):
-                    value = as_column(value)[key]
-            nelem = len(key)
+                return libcudf.copying.boolean_mask_scatter(
+                    [value], [self], key
+                )[0]._with_type_metadata(self.dtype)
+            else:
+                return libcudf.copying.scatter(
+                    value, key, self
+                )._with_type_metadata(self.dtype)
+        except RuntimeError as e:
+            if "out of bounds" in str(e):
+                raise IndexError(
+                    f"index out of bounds for column of size {len(self)}"
+                ) from e
+            raise
 
-        if is_scalar(value):
-            value = cudf.Scalar(value, dtype=self.dtype)
-        else:
+    def _check_scatter_key_length(
+        self, nelem: int, value: Union[cudf.core.scalar.Scalar, ColumnBase]
+    ):
+        """`nelem` is the number of keys to scatter. Should equal to the
+        number of rows in ``value`` if ``value`` is a column.
+        """
+        if isinstance(value, ColumnBase):
             if len(value) != nelem:
                 msg = (
                     f"Size mismatch: cannot set value "
                     f"of size {len(value)} to indexing result of size "
                     f"{nelem}"
                 )
                 raise ValueError(msg)
-            value = as_column(value).astype(self.dtype)
-
-        if (
-            isinstance(key, slice)
-            and (key_stride == 1 or key_stride is None)
-            and not is_scalar(value)
-        ):
-
-            out = libcudf.copying.copy_range(
-                value, self, 0, nelem, key_start, key_stop, False
-            )
-        else:
-            try:
-                if not isinstance(key, Column):
-                    key = as_column(key)
-                if not is_scalar(value) and not isinstance(value, Column):
-                    value = as_column(value)
-                out = libcudf.copying.scatter(
-                    value, key, self
-                )._with_type_metadata(self.dtype)
-            except RuntimeError as e:
-                if "out of bounds" in str(e):
-                    raise IndexError(
-                        f"index out of bounds for column of size {len(self)}"
-                    ) from e
-                raise
-
-        self._mimic_inplace(out, inplace=True)
 
     def fillna(
         self: T,
@@ -2237,7 +2281,7 @@ def arange(
     stop: Union[int, float] = None,
     step: Union[int, float] = 1,
     dtype=None,
-) -> ColumnBase:
+) -> "cudf.core.column.NumericalColumn":
     """
     Returns a column with evenly spaced values within a given interval.
 

python/cudf/cudf/tests/test_setitem.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2018-2021, NVIDIA CORPORATION.
+# Copyright (c) 2018-2022, NVIDIA CORPORATION.
 
 import numpy as np
 import pandas as pd
@@ -187,6 +187,33 @@ def test_column_set_equal_length_object_by_mask():
     assert_eq(cudf.Series(data), cudf.Series([100, 0, 300, 1, 500]))
 
 
+def test_column_set_unequal_length_object_by_mask():
+    data = [1, 2, 3, 4, 5]
+    replace_data_1 = [8, 9]
+    replace_data_2 = [8, 9, 10, 11]
+    mask = [True, True, False, True, False]
+
+    psr = pd.Series(data)
+    gsr = cudf.Series(data)
+    assert_exceptions_equal(
+        psr.__setitem__,
+        gsr.__setitem__,
+        ([mask, replace_data_1], {}),
+        ([mask, replace_data_1], {}),
+        compare_error_message=False,
+    )
+
+    psr = pd.Series(data)
+    gsr = cudf.Series(data)
+    assert_exceptions_equal(
+        psr.__setitem__,
+        gsr.__setitem__,
+        ([mask, replace_data_2], {}),
+        ([mask, replace_data_2], {}),
+        compare_error_message=False,
+    )
+
+
 def test_categorical_setitem_invalid():
     ps = pd.Series([1, 2, 3], dtype="category")
     gs = cudf.Series([1, 2, 3], dtype="category")