#36750: dumpdata's output of m2m values is not deterministic
-------------------------------------+-------------------------------------
Reporter: Jacob Walls | Type: Bug
Status: new | Component: Core
| (Serialization)
Version: dev | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Recent failure of `main-random` CI job reveals that dumpdata's output of
m2m values is not deterministic:
{{{
./runtests.py fixtures --shuffle 7825542710 --settings=test_postgres -k
forward -v2
}}}
{{{
test_forward_reference_fk
(fixtures.tests.ForwardReferenceTests.test_forward_reference_fk) ... ok
test_forward_reference_m2m
(fixtures.tests.ForwardReferenceTests.test_forward_reference_m2m) ... ok
test_forward_reference_fk_natural_key
(fixtures.tests.ForwardReferenceTests.test_forward_reference_fk_natural_key)
... ok
test_forward_reference_m2m_natural_key
(fixtures.tests.ForwardReferenceTests.test_forward_reference_m2m_natural_key)
... FAIL
======================================================================
FAIL: test_forward_reference_m2m_natural_key
(fixtures.tests.ForwardReferenceTests.test_forward_reference_m2m_natural_key)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/Users/jwalls/django/tests/fixtures/tests.py", line 1308, in
test_forward_reference_m2m_natural_key
self._dumpdata_assert(
~~~~~~~~~~~~~~~~~~~~~^
["fixtures"],
^^^^^^^^^^^^^
...<8 lines>...
natural_foreign_keys=True,
^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/Users/jwalls/django/tests/fixtures/tests.py", line 127, in
_dumpdata_assert
self.assertJSONEqual(command_output, output)
~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Lists differ: [{'mo[94 chars] [['t3'], ['t2']]}},
{'model': 'fixtures.natur[179 chars][]}}] != [{'mo[94 chars] [['t2'],
['t3']]}}, {'model': 'fixtures.natur[179 chars][]}}]
First differing element 0:
{'mod[49 chars]: 't1', 'other_thing': None, 'other_things': [['t3'],
['t2']]}}
{'mod[49 chars]: 't1', 'other_thing': None, 'other_things': [['t2'],
['t3']]}}
[{'fields': {'key': 't1',
'other_thing': None,
- 'other_things': [['t3'], ['t2']]},
? --------
+ 'other_things': [['t2'], ['t3']]},
? ++++++++
'model': 'fixtures.naturalkeything'},
{'fields': {'key': 't2', 'other_thing': None, 'other_things': []},
'model': 'fixtures.naturalkeything'},
{'fields': {'key': 't3', 'other_thing': None, 'other_things': []},
'model': 'fixtures.naturalkeything'}]
----------------------------------------------------------------------
Ran 4 tests in 0.071s
FAILED (failures=1)
Used shuffle seed: 7825542710 (given)
}}}
----
In the spirit of #24558 and #10381, I'm suggesting to make this
deterministic instead of fiddling with the test.
A naive diff just adding ordering by "pk" fixes the failure ...:
{{{#!py
diff --git a/django/core/serializers/python.py
b/django/core/serializers/python.py
index 2929874b01..496d3a5ba6 100644
--- a/django/core/serializers/python.py
+++ b/django/core/serializers/python.py
@@ -74,7 +74,7 @@ class Serializer(base.Serializer):
return value.natural_key()
def queryset_iterator(obj, field):
- attr = getattr(obj, field.name)
+ attr = getattr(obj, field.name).order_by("pk") # !!!
not right
chunk_size = (
2000 if getattr(attr, "prefetch_cache_name",
None) else None
)
}}}
... but to be mergeable, the patch would need to:
- get the default ordering from somewhere better (through model? target
model?), instead of hardcoding "pk"
- check for all locations in the python and xml serializers that might
need this change
--
Ticket URL: <https://code.djangoproject.com/ticket/36750>
Django <https://code.djangoproject.com/>
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