[ARROW-13474] [C++][Python] PyArrow crash when filter/take empty Extension array

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0, 4.0.0, 4.0.1
• Fix Version/s: 6.0.0
• Component/s: C++, Python
• Labels: pull-request-available
• Environment: Python 3.7, Ubuntu 20.04
• External issue URL: https://github.com/apache/arrow/issues/29137
• Assignee: Joris Van den Bossche
• Reporter: Paul Balanca
• Created: 28/Jul/21 11:22
• Updated: 11/Jan/23 08:33
• Resolved: 28/Sep/21 11:29

Description

PyArrow is crashing when applying `filter` or `take` on already empty extension arrays.

The bug can be reproduced with the documentation example:

import pyarrow as pa

class Point3DArray(pa.ExtensionArray):
    def to_numpy_array(self):
        return self.storage.flatten().to_numpy().reshape((-1, 3))


class Point3DType(pa.PyExtensionType):
    def __init__(self):
        pa.PyExtensionType.__init__(self, pa.list_(pa.float32(), 3))

    def __reduce__(self):
        return Point3DType, ()

    def __arrow_ext_class__(self):
        return Point3DArray

storage = pa.array([[1, 2, 3], [4, 5, 6]], pa.list_(pa.float32(), 3))
arr = pa.ExtensionArray.from_storage(Point3DType(), storage)
arr = arr.filter(pa.array([False, False]))

# Crashing here...
arr.filter(pa.array([], pa.bool_()))
# Crashing as well...
arr.take(pa.array([], pa.int32()))

The underlying issue seems to be that the function `nulls` is not implemented for extension types in the C++ codebase: https://github.com/apache/arrow/blob/6db88a9e946c98c59f179210a70bc05ef6a0a296/cpp/src/arrow/array/util.cc#L472

Issue Links

• links to: GitHub Pull Request #11227