#25947: Query's str() method fails when 'default' database is empty
-------------------------------------+-------------------------------------
Reporter: liboz | Owner: jayvynl
Type: Bug | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Natalia Bidart):
Following a chat with Sarah about this ticket and PR, I can confirm this
issue is still valid. For the sake of explicitness, these are the steps to
reproduce the original report:
0. ensure that you have latest django installed and venv enabled if that
applies
1. create an empty test project `django-admin startproject projectmultidb`
2. change into the project directory `cd projectmultidb`
3. create a router definition, for example in
`dbrouter.testrouter.TestRouter`, use the router as provided above (no
`(object)` inheritance though)
{{{#!python
class TestRouter:
db_alias = "test"
def db_for_read(self, model, **hints):
return self.db_alias
def db_for_write(self, model, **hints):
return self.db_alias
def allow_relation(self, obj1, obj2, **hints):
return True
def allow_migrate(self, db, app_label, model_name=None, **hints):
return True
}}}
4. tweak the settings to the following:
{{{#!python
DATABASE_ROUTERS = ["dbrouter.testrouter.TestRouter"]
DATABASES = {
"default": {},
'test': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': BASE_DIR / 'test.sqlite3',
},
}
}}}
5. Double check no migrations are pending `python -Wall manage.py
makemigrations` should return `No changes detected`
6. Apply migrations from apps `python -Wall manage.py migrate
--database=test` with output:
{{{
Operations to perform:
Apply all migrations: admin, auth, contenttypes, sessions
Running migrations:
Applying contenttypes.0001_initial... OK
...
Applying auth.0012_alter_user_first_name_max_length... OK
Applying sessions.0001_initial... OK
}}}
7. Start a new app `testapp`, add a `Question` model as described above,
generate migration, and apply it:
{{{
(django-3.12) [projectmultidb]$ python -Wall manage.py startapp testapp
(django-3.12) [projectmultidb]$ python -Wall manage.py makemigrations
Migrations for 'testapp':
testapp/migrations/0001_initial.py
+ Create model Question
(django-3.12) [projectmultidb]$ python -Wall manage.py migrate
--database=test
Operations to perform:
Apply all migrations: admin, auth, contenttypes, sessions, testapp
Running migrations:
Applying testapp.0001_initial... OK
}}}
8. Open the shell `python -Wall manage.py shell` and run:
{{{
In [1]: from django.db import connections
In [2]: from testapp.models import Question
In [3]: Question.objects.all()
Out[3]: <QuerySet []>
In [4]: connections["test"].queries
Out[4]:
[{'sql': 'SELECT "testapp_question"."id",
"testapp_question"."question_text", "testapp_question"."pub_date" FROM
"testapp_question" LIMIT 21',
'time': '0.001'}]
In [5]: print(Question.objects.all().query)
---------------------------------------------------------------------------
ImproperlyConfigured Traceback (most recent call
last)
...
ImproperlyConfigured: settings.DATABASES is improperly configured. Please
supply the ENGINE value. Check settings documentation for more details.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25947#comment:12>
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