[Serialization] Fix reference counting of numpy arrays created in custom serialializer

[asfimport]

The problem happens with the following code:

import numpy as np
import pyarrow
import sys

class Bar(object):
    pass

def bar_custom_serializer(obj):
    x = np.zeros(4)
    return x

def bar_custom_deserializer(serialized_obj):
    return serialized_obj

pyarrow._default_serialization_context.register_type(Bar, "Bar", pickle=False, custom_serializer=bar_custom_serializer, custom_deserializer=bar_custom_deserializer)

pyarrow.serialize(Bar())

After execution of pyarrow.serialize, the interpreter crashes in the garbage collection routine.

This happens if a numpy array is returned in the custom serializer but there is no other reference to the numpy array. The reason this is not a problem in the current code is that so far we haven't created new numpy arrays in the custom serializer.

I think the problem here is that the numpy array hits reference count zero between the end of SerializeSequences in python_to_arrow.cc and the call to NdarrayToTensor. I'll push a fix later today, which just increases and decreases the reference counts at the appropriate places.

Reporter: Philipp Moritz / @pcmoritz
Assignee: Philipp Moritz / @pcmoritz

PRs and other links:

• GitHub Pull Request #1220

_{Note: This issue was originally created as ARROW-1695. Please see the migration documentation for further details.}

[asfimport]

Philipp Moritz / @pcmoritz:
Issue resolved by pull request 1220
#1220