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Fix HistoricForeignKey when used together with prefetch_related() #1159

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Fix HistoricForeignKey when used together with prefetch_related() #1159

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1 change: 1 addition & 0 deletions CHANGES.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ Changes
Unreleased
----------

- Fixed ``HistoricForeignKey`` behaviour when used together with ``prefetch_related()``
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It would be useful being a little more explicit on what the bug used to be; also, adding the issue number 🙂

Suggested change
- Fixed ``HistoricForeignKey`` behaviour when used together with ``prefetch_related()``
- Fixed ``HistoricForeignKey``'s behaviour when used together with
``prefetch_related()``, which caused some related objects to be missing (gh-1152)


3.3.0 (2023-03-08)
------------------
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2 changes: 1 addition & 1 deletion simple_history/models.py
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Expand Up @@ -860,7 +860,7 @@ def get_queryset(self):
)
else:
queryset = super().get_queryset()
return self._apply_rel_filters(queryset)
return queryset

return create_reverse_many_to_one_manager(
HistoricRelationModelManager, self.rel
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93 changes: 93 additions & 0 deletions simple_history/tests/tests/test_models.py
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Expand Up @@ -2545,3 +2545,96 @@ def test_historic_to_historic(self):
)[0]
pt1i = pt1h.instance
self.assertEqual(pt1i.organization.name, "original")

def test_non_historic_to_historic_prefetch(self):
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Please add a docstring detailing a little more explicitly what the test case is testing 🙂 E.g. something like this: (feel free to adjust the text)

Suggested change
def test_non_historic_to_historic_prefetch(self):
def test_non_historic_to_historic_prefetch(self):
"""Test that the field works properly with ``prefetch_related()`` when defined
on a model *without* history tracking, and with the ``to`` arg set to a model
*with* history tracking."""

The same goes for the two test cases below.

org1 = TestOrganizationWithHistory.objects.create(name="org1")
org2 = TestOrganizationWithHistory.objects.create(name="org2")

p1 = TestParticipantToHistoricOrganization.objects.create(
name="p1", organization=org1
)
p2 = TestParticipantToHistoricOrganization.objects.create(
name="p2", organization=org1
)
p3 = TestParticipantToHistoricOrganization.objects.create(
name="p3", organization=org2
)
p4 = TestParticipantToHistoricOrganization.objects.create(
name="p4", organization=org2
)

with self.assertNumQueries(2):
record1, record2 = TestOrganizationWithHistory.objects.prefetch_related(
"participants"
).all()
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all() after prefetch_related() (or most other queryset-returning methods) is unnecessary.

Suggested change
).all()
)

The same goes for the similar calls to all() in the two test cases below.


self.assertListEqual(
[p.name for p in record1.participants.all()],
[p1.name, p2.name],
)
self.assertListEqual(
[p.name for p in record2.participants.all()],
[p3.name, p4.name],
)

def test_historic_to_non_historic_prefetch(self):
org1 = TestOrganization.objects.create(name="org1")
org2 = TestOrganization.objects.create(name="org2")

p1 = TestHistoricParticipantToOrganization.objects.create(
name="p1", organization=org1
)
p2 = TestHistoricParticipantToOrganization.objects.create(
name="p2", organization=org1
)
p3 = TestHistoricParticipantToOrganization.objects.create(
name="p3", organization=org2
)
p4 = TestHistoricParticipantToOrganization.objects.create(
name="p4", organization=org2
)

with self.assertNumQueries(2):
record1, record2 = TestOrganization.objects.prefetch_related(
"participants"
).all()

self.assertListEqual(
[p.name for p in record1.participants.all()],
[p1.name, p2.name],
)
self.assertListEqual(
[p.name for p in record2.participants.all()],
[p3.name, p4.name],
)

def test_historic_to_historic_prefetch(self):
org1 = TestOrganizationWithHistory.objects.create(name="org1")
org2 = TestOrganizationWithHistory.objects.create(name="org2")

p1 = TestHistoricParticipanToHistoricOrganization.objects.create(
name="p1", organization=org1
)
p2 = TestHistoricParticipanToHistoricOrganization.objects.create(
name="p2", organization=org1
)
p3 = TestHistoricParticipanToHistoricOrganization.objects.create(
name="p3", organization=org2
)
p4 = TestHistoricParticipanToHistoricOrganization.objects.create(
name="p4", organization=org2
)

with self.assertNumQueries(2):
record1, record2 = TestOrganizationWithHistory.objects.prefetch_related(
"historic_participants"
).all()

self.assertListEqual(
[p.name for p in record1.historic_participants.all()],
[p1.name, p2.name],
)
self.assertListEqual(
[p.name for p in record2.historic_participants.all()],
[p3.name, p4.name],
)