#34440: AND operator on queryset with joins gives wrong results
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Reporter: Guillaume LEBRETON | Owner: David
Type: | Sanders
Cleanup/optimization | Status: assigned
Component: Documentation | Version: 4.1
Severity: Normal | Resolution:
Keywords: orm and operato | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Guillaume LEBRETON):
Replying to [comment:1 David Sanders]:
> Hi,
>
> Yes 2 querysets joined with the & operator are effectively chained
together. Whilst I can see that it can be misleading in this case the
linked example shown isn't technically "wrong", though I'd recommend that
the docs be updated here to avoid confusion.
>
> If you'd like to propose that there be some way to join querysets in the
way you'd like I'd encourage you to start a discussion on the Django
developer's mailing list: DevelopersMailingList.
Hello David, thanks for your help. Your are right, chained filters and
multiple kwargs filters are equivalent ONLY when there is no joins
involved, and that was misleading for me.
Here is another test to show that in case of no joins these 3 queries are
equivalent, where it's not the case with joins.
{{{
def test_combine_AND_without_join(self):
expected_result = [
{'name': 'age'}
]
with self.subTest('single filter qs'):
qs = QuantitativeAttribute.objects.filter(name='age',
value=27)
self.assertQuerysetEqual(qs.values('name'), expected_result)
with self.subTest('combined AND filter qs'):
qs1 = QuantitativeAttribute.objects.filter(name='age')
qs2 = QuantitativeAttribute.objects.filter(value=27)
qs = qs1 & qs2
self.assertQuerysetEqual(qs.values('name'), expected_result)
with self.subTest('combined AND filter qs'):
qs =
QuantitativeAttribute.objects.filter(name='age').filter(value=27)
self.assertQuerysetEqual(qs.values('name'), expected_result)
}}}
Perhaps one line of text in the doc should explain that difference with
joins, along with your modification ?
Something like `Model.objects.filter(x=1, y=2) <=>
Model.objects.filter(x=1).filter(y=2)`
but `Model.objects.filter(related__x=1, related__y=1) !=
Model.objects.filter(related__x=1).filter(related__y=1)`
--
Ticket URL: <https://code.djangoproject.com/ticket/34440#comment:5>
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