#25693: Data loss if a ManyToManyField is shadowed by Prefetch
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Reporter: Ian-Foote | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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With two models:
{{{#!python
class Book(Model):
name = CharField(max_length=100)
class Author(Model):
books = ManyToManyField(Book)
}}}
it is possible to create a prefetch query that loses data from
Author.books:
{{{#!python
poems = Book.objects.filter(name='Poems')
Author.objects.prefetch_related(
Prefetch('books', queryset=poems, to_attr='books'),
)
}}}
When this queryset is evaluated, each Author's books is overridden by the
poems queryset.
--
Ticket URL: <https://code.djangoproject.com/ticket/25693>
Django <https://code.djangoproject.com/>
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