Hi filias,
I personally didn't know one could define a reverse foreign key this way and
I doubt this use case is covered by the test suite. I'm afraid it worked for
Django < 1.8 by chance since it's not documented you can re-use the
implicitly created intermediary model as a `through` argument. I suspect
this
might be due to the `_meta`[1] refactoring that happened in 1.8.
May I ask you why you don't simply define a `related_name`[2] if you simply
want to have a different reverse relationship name?
class Pizza(models.Model):
pass
class Topping(models.Model):
all_pizzas = models.ManyToManyField(
Pizza, related_name='available_toppings',
verbose_name='available pizzas'
)
Cheers,
Simon
[1] https://docs.djangoproject.com/en/1.8/releases/1.8/#model-meta-api
[2]
https://docs.djangoproject.com/en/1.8/ref/models/fields/#django.db.models.ManyToManyField.related_name
Le vendredi 4 décembre 2015 07:08:51 UTC-5, filias a écrit :
>
> Indeed something in the project's code must be wrong but it is not the
> bi-directional ManyToMany as this has been working in django 1.4, 1.5, 1.6
> and 1.7. One might want to had the ManyToMany in both models so to be able
> to add more information, as it is stated in the django docs
> https://docs.djangoproject.com/en/1.9/topics/db/models/#extra-fields-on-many-to-many-relationships
>
> in my case I just want the field to have a different name. I am thinking of
> using a property but I got into some troubles with my code when I did that,
> specifically the migration to remove the all_pizzas field crashes.
>
> I have created a new project with only those 2 models and it seems to work
> correctly, so the problem is somehow related to our test runner (py.test)
> and something else which I still don't know.
>
> My models.py file looks like this:
> from django.db import models
>
>
> class Pizza(models.Model):
> available_toppings = models.ManyToManyField('Topping')
>
>
> class Topping(models.Model):
> all_pizzas = models.ManyToManyField(Pizza,
> through=Pizza.available_toppings.through, verbose_name='available pizzas')
>
> I will continue investigating.
>
> On Friday, December 4, 2015 at 11:31:19 AM UTC+1, Remco Gerlich wrote:
>>
>> One, from that error message alone I can't figure out what is happening
>> and why when you run tests, so I can't help there.
>>
>> But two: you don't have a ManyToManyField, you have TWO ManyToManyFields.
>> If you define a many to many field on one model, than it's automatically
>> also defined on the other (if you only have the one on Pizza, then you can
>> do topping.pizza_set.all() from the other side.
>>
>> So your current code is almost certainly wrong, but if these are your
>> exact models than I don't think they are related to your error.
>>
>> Remco
>>
>> On Fri, Dec 4, 2015 at 9:54 AM, filias <filipa....@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> I have recently upgraded to sjango 1.8 and I have 2 models with a
>>> bi-directional ManyToMany field. It looks like this
>>>
>>> class Pizza(Model):
>>> available_toppings = ManyToManyField('Topping')
>>>
>>> class Topping(Model):
>>> all_pizzas = ManyToManyField(Pizza,
>>> through=Pizza.available_stoppings.through, verbose_name='available pizzas')
>>>
>>> Everything was fine in django 1.7 but right now when running tests,
>>> specifically when creating the test database, I get this exception:
>>>
>>> self = <django.db.backends.sqlite3.base.SQLiteCursorWrapper object at
>>> 0x7fd24fca4b00>
>>>
>>> def execute(self, query, params=None):
>>> if params is None:
>>>
>>> > return Database.Cursor.execute(self, query)
>>> E OperationalError: table "products_pizza_available_toppings"
>>> already exists
>>>
>>> So it looks like the creation of the test database is trying to
>>> re-create the intermediate table for the ManyToMany.
>>>
>>> I do not get any exception when running my site.
>>>
>>> Does anyone know how can I fix this?
>>>
>>> Thank you in advance
>>>
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>>
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