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Refs #27718 -- Doc'd and tested QuerySet.exists() for combined querysets. 

Supported since 84c1826ded.
This commit is contained in:
David-Wobrock 2020-11-13 22:34:16 +01:00 committed by Mariusz Felisiak
parent 4cce1d13cf
commit 7b42d34646
2 changed files with 28 additions and 5 deletions
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10
docs/ref/models/querysets.txt
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@ -917,11 +917,11 @@ resulting ``QuerySet``. For example::
>>> qs1.union(qs2).order_by('name') >>> qs1.union(qs2).order_by('name')
In addition, only ``LIMIT``, ``OFFSET``, ``COUNT(*)``, ``ORDER BY``, and In addition, only ``LIMIT``, ``OFFSET``, ``COUNT(*)``, ``ORDER BY``, and
specifying columns (i.e. slicing, :meth:`count`, :meth:`order_by`, and specifying columns (i.e. slicing, :meth:`count`, :meth:`exists`,
:meth:`values()`/:meth:`values_list()`) are allowed on the resulting :meth:`order_by`, and :meth:`values()`/:meth:`values_list()`) are allowed
``QuerySet``. Further, databases place restrictions on what operations are on the resulting ``QuerySet``. Further, databases place restrictions on
allowed in the combined queries. For example, most databases don't allow what operations are allowed in the combined queries. For example, most
``LIMIT`` or ``OFFSET`` in the combined queries. databases don't allow ``LIMIT`` or ``OFFSET`` in the combined queries.
``intersection()`` ``intersection()``
~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~

23
tests/queries/test_qs_combinators.py
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@ -254,6 +254,29 @@ class QuerySetSetOperationTests(TestCase):
qs2 = Number.objects.filter(num__lte=5) qs2 = Number.objects.filter(num__lte=5)
self.assertEqual(qs1.intersection(qs2).count(), 1) self.assertEqual(qs1.intersection(qs2).count(), 1)
def test_exists_union(self):
qs1 = Number.objects.filter(num__gte=5)
qs2 = Number.objects.filter(num__lte=5)
self.assertIs(qs1.union(qs2).exists(), True)
def test_exists_union_empty_result(self):
qs = Number.objects.filter(pk__in=[])
self.assertIs(qs.union(qs).exists(), False)
@skipUnlessDBFeature('supports_select_intersection')
def test_exists_intersection(self):
qs1 = Number.objects.filter(num__gt=5)
qs2 = Number.objects.filter(num__lt=5)
self.assertIs(qs1.intersection(qs1).exists(), True)
self.assertIs(qs1.intersection(qs2).exists(), False)
@skipUnlessDBFeature('supports_select_difference')
def test_exists_difference(self):
qs1 = Number.objects.filter(num__gte=5)
qs2 = Number.objects.filter(num__gte=3)
self.assertIs(qs1.difference(qs2).exists(), False)
self.assertIs(qs2.difference(qs1).exists(), True)
def test_get_union(self): def test_get_union(self):
qs = Number.objects.filter(num=2) qs = Number.objects.filter(num=2)
self.assertEqual(qs.union(qs).get().num, 2) self.assertEqual(qs.union(qs).get().num, 2)