#35309: Remove Order by on models when prefetching by id
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Reporter: Laurent | Owner: nobody
Lyaudet |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: 5.0
layer (models, ORM) |
Severity: Normal | Keywords: prefetch order_by
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Hello,
I don't know if the "bug" is still here with Django 5.
But on my version of Django, I have the following "bug" :
Assume you have the following code :
{{{#!python
class A(models.Model):
name = models.CharField(max_length=200)
class Meta:
ordering = ["name"]
class B(models.Model):
a = models.ForeignKey(A, related_name="bs", on_delete=models.CASCADE)
a1 = A.objects.create(name="a1")
a2 = A.objects.create(name="a2")
a3 = A.objects.create(name="a3")
a4 = A.objects.create(name="a4")
a5 = A.objects.create(name="a5")
a6 = A.objects.create(name="a6")
a7 = A.objects.create(name="a7")
b1 = B.objects.create(a=a1)
b2 = B.objects.create(a=a2)
b3 = B.objects.create(a=a3)
b4 = B.objects.create(a=a4)
b5 = B.objects.create(a=a5)
b6 = B.objects.create(a=a6)
b7 = B.objects.create(a=a7)
bs = B.objects.all().prefetch_related("a")
}}}
The prefetch of as will use the order by and add useless charge on the DB
server.
There may be other cases than ForeignKey where the order by is useless.
But since OneToOne inherits from ForeignKey, I don't see anything else
right now.
Hence, I request this enhancement, please :)
#ClimateChangeBrake
Best regards,
Laurent Lyaudet
--
Ticket URL: <https://code.djangoproject.com/ticket/35309>
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