#28107: Can't perform annotation on related table when un-managed model is
backed
by a DB view
-------------------------------------+-------------------------------------
Reporter: powderflask | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: QuerySet.extra | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Simon Charette):
From what I understood you are still on 1.8 but this patch will only be
available in a couple of months when 2.0 is released.
To get this fixed on your side in the mean time you'll have to define your
own `django.db.backends.postgresql.base.DatabaseWrapper` subclass but it's
not as intimidating as it sounds.
Simply define a `DatabaseWrapper` subclass in a `chosen_module_name.base`
module that extends the aforementioned class and set it's `features_class`
attribute to a subclass of
`django.db.backends.postgresql.features.DatabaseFeatures` with
`allows_group_by_selected_pks = False`
{{{
django.db.backends.postgresql import base, features
class DatabaseWrapper(base.DatabaseWrapper):
class features_class(features.DatabaseFeatures):
allows_group_by_selected_pks = False
}}}
Note that this disable the optimization all together. If you want to keep
the optimization for managed models you'll have to define your own
`SQLCompiler` subclass and override the `collapse_group_by` method which
is a bit harder. I suggest you have a look
[https://github.com/django/django/blob/e7afef13f594eb667f2709c0ef7bca98452ab32b/django/db/backends/mysql/operations.py#L10
how it's done for the MySQL backend] to figure it out.
I suggest you have a look at how [https://github.com/carljm/django-
transaction-hooks django-transaction-hooks] did it if you need a more
concrete example.
--
Ticket URL: <https://code.djangoproject.com/ticket/28107#comment:12>
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