#32775: LiveServerTestCase fails when query expressions are used for model
ordering
-----------------------------------+------------------------------------
Reporter: Gergely Kalmár | Owner: nobody
Type: Bug | Status: new
Component: Testing framework | Version: 3.2
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-----------------------------------+------------------------------------
Changes (by Simon Charette):
* stage: Unreviewed => Accepted
Comment:
You'll want to make sure to generate migrations for the app containing
these models otherwise you won't be able to reproduce.
This bug is two fold. First we likely just want to have the querysets
generated during serialization order by the primary key without involving
possible related object semantic
{{{#!python
diff --git a/django/db/backends/base/creation.py
b/django/db/backends/base/creation.py
index 81cb34bd9f..f49c31edaf 100644
--- a/django/db/backends/base/creation.py
+++ b/django/db/backends/base/creation.py
@@ -129,7 +129,7 @@ def get_objects():
):
queryset = model._base_manager.using(
self.connection.alias,
- ).order_by(model._meta.pk.name)
+ ).order_by('pk')
yield from queryset.iterator()
# Serialize to a string
out = StringIO()
}}}
The above happens to address the reported crash but it doesn't deal with
the fundamental issue which is that
`Referent.objects.order_by('reference')` crashes if
`Referred.Meta.ordering` contains expressions because they won't be
transposed to the origin of the queryset (e.g. `Lower('id') ->
Lower('order__id')` in the reported case). It can be reproduced with the
same set of models and the following test
{{{#!python
from django.test import TestCase
from .models import Offer
class Test(TestCase):
def test_case(self):
list(Offer.objects.order_by('order'))
}}}
The issue lies in `SQLCompiler.find_ordering_name` but
[https://github.com/django/django/blob/5e04e84d67da8163f365e9f5fcd169e2630e2873/django/db/models/sql/compiler.py#L773-L774
is not trivial to address] as we'd need a way to prefix all field
references in an `Expression` so I'd suggest we raise a
`NotImplementedError` instead for now. [https://djangoci.com/job/django-
coverage/HTML_20Coverage_20Report/_home_jenkins_workspace_django-
coverage_django_db_models_sql_compiler_py.html#t774 Not sure when this
path is covered by the suite] but I would assume it would only work when
MTI inheritance is involved and referenced field references don't need to
be prefixed as they are inherited?
--
Ticket URL: <https://code.djangoproject.com/ticket/32775#comment:2>
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