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Fixed #24508 -- Made annotations commutative
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@ -238,7 +238,16 @@ class BaseExpression(object):
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"""
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Attempts to infer the output type of the expression. If the output
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fields of all source fields match then we can simply infer the same
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type here.
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type here. This isn't always correct, but it makes sense most of the
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time.
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Consider the difference between `2 + 2` and `2 / 3`. Inferring
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the type here is a convenience for the common case. The user should
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supply their own output_field with more complex computations.
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If a source does not have an `_output_field` then we exclude it from
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this check. If all sources are `None`, then an error will be thrown
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higher up the stack in the `output_field` property.
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"""
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if self._output_field is None:
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sources = self.get_source_fields()
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@ -246,8 +255,9 @@ class BaseExpression(object):
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if num_sources == 0:
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self._output_field = None
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else:
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self._output_field = sources[0]
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for source in sources:
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if self._output_field is None:
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self._output_field = source
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if source is not None and not isinstance(self._output_field, source.__class__):
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raise FieldError(
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"Expression contains mixed types. You must set output_field")
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@ -182,6 +182,14 @@ class NonAggregateAnnotationTestCase(TestCase):
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sum_rating=Sum('rating')
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).filter(sum_rating=F('nope')))
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def test_combined_annotation_commutative(self):
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book1 = Book.objects.annotate(adjusted_rating=F('rating') + 2).get(pk=self.b1.pk)
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book2 = Book.objects.annotate(adjusted_rating=2 + F('rating')).get(pk=self.b1.pk)
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self.assertEqual(book1.adjusted_rating, book2.adjusted_rating)
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book1 = Book.objects.annotate(adjusted_rating=F('rating') + None).get(pk=self.b1.pk)
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book2 = Book.objects.annotate(adjusted_rating=None + F('rating')).get(pk=self.b1.pk)
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self.assertEqual(book1.adjusted_rating, book2.adjusted_rating)
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def test_update_with_annotation(self):
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book_preupdate = Book.objects.get(pk=self.b2.pk)
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Book.objects.annotate(other_rating=F('rating') - 1).update(rating=F('other_rating'))
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