Correctly set bitmask size in from_column_view

python/cudf/cudf/_lib/column.pyx

@@ -155,6 +155,7 @@ cdef class Column:
             )
 
         if value is not None:
+            # bitmask size must be relative to offset = 0 data.
             required_size = bitmask_allocation_size_bytes(self.base_size)
             if value.size < required_size:
                 error_msg = (
@@ -599,7 +600,7 @@ cdef class Column:
                     mask = as_buffer(
                         rmm.DeviceBuffer(
                             ptr=mask_ptr,
-                            size=bitmask_allocation_size_bytes(size+offset)
+                            size=bitmask_allocation_size_bytes(base_size)
                         )
                     )
             else:

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

@@ -28,10 +28,10 @@ class StructColumn(ColumnBase):
 
     @property
     def base_size(self):
-        if not self.base_children:
-            return 0
-        else:
+        if self.base_children:
             return len(self.base_children[0])
+        else:
+            return self.size + self.offset
 
     def to_arrow(self):
         children = [

python/cudf/cudf/tests/test_struct.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2020-2022, NVIDIA CORPORATION.
+# Copyright (c) 2020-2023, NVIDIA CORPORATION.
 
 import numpy as np
 import pandas as pd
@@ -392,3 +392,20 @@ def test_struct_with_null_memory_usage():
 
     s[2:4] = None
     assert s.memory_usage() == 272
+
+
+@pytest.mark.parametrize(
+    "indices",
+    [slice(0, 3), slice(1, 4), slice(None, None, 2), slice(1, None, 2)],
+    ids=[":3", "1:4", "0::2", "1::2"],
+)
+@pytest.mark.parametrize(
+    "values",
+    [[None, {}, {}, None], [{}, {}, {}, {}]],
+    ids=["nulls", "no_nulls"],
+)
+def test_struct_empty_children_slice(indices, values):
+    s = cudf.Series(values)
+    actual = s.iloc[indices]
+    expect = cudf.Series(values[indices], index=range(len(values))[indices])
+    assert_eq(actual, expect)