#36442: Reusing same instance of FilteredRelations in multiple queries result in
django.core.exceptions.FieldError: Cannot resolve keyword
-------------------------------------+-------------------------------------
Reporter: Viliam Mihálik | Type:
| Uncategorized
Status: new | Component: Database
| layer (models, ORM)
Version: 5.2 | Severity: Normal
Keywords: FilteredRelation, | Triage Stage:
ORM | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Example test case that should pass, used in FilteredRelationTests
{{{
def test_reuse_same_filtered_relation(self):
borrower = Borrower.objects.create(name="Jenny")
Reservation.objects.create(
borrower=borrower,
book=self.book1,
state=Reservation.STOPPED,
)
condition = Q(book__reservation__state=Reservation.STOPPED)
my_reserved_books = FilteredRelation(
"book__reservation",
condition=condition
)
first_result = list(Author.objects.annotate(
my_reserved_books=my_reserved_books,
))
self.assertEqual(my_reserved_books.condition, condition)
# AssertionError: <Q: (AND: ('my_reserved_books__state', 'stopped'))>
!= <Q: (AND: ('book__reservation__state', 'stopped'))>
second_result = list(Author.objects.annotate(
my_reserved_books=my_reserved_books,
))
# django.core.exceptions.FieldError: Cannot resolve keyword
'my_reserved_books' into field. Choices are: book, content_object,
content_type, content_type_id, favorite_books, id, name, object_id
}}}
When you reuse same `FilteredRelation` in different queries, internal
`FilteredRelation.condition` is changed and no longer works.
This same code works on Django 4.x. This change was introduced by fixing
of bug #33766
Based on discussion in #33766 it was intended but breaking for us after
upgrading from 4 -> 5.
In order to get this working is to `my_reserved_books.clone()` clone
annotate before using.
--
Ticket URL: <https://code.djangoproject.com/ticket/36442>
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