Hi Ram,
I don't have a complete solution for you but I suggest you take a look at
the
django.db.models.fields.related.ForeignObject class.
If I'm not mistaken it should allow you to define multi-column relationships
on both your Article and PublisherMediumBilling models and refer to them
using
the `select_related()` and `prefetch_related()``API while the later uses
Python
to perform in-memory JOINs.
class Article(models.Model):
publisher = ForeignKey(Publisher, related_name='articles')
medium = ForeignKey(Medium)
billing = ForeignObject(
'PublisherMediumBilling', from_fields=['publisher', 'medium'],
to_fields=['publisher', 'medium']
)
publisher.articles.select_related('billing')
Cheers,
Simon
Le samedi 18 juin 2016 07:09:03 UTC-4, Ram Jayaraman a écrit :
>
> I apologize if this is an old question, I did search SO/google for a good
> few hours.
>
> I have the following models.
>
> Publisher()
> name = CharField()
>
> Medium()
> name = CharField()
>
> Article()
> publisher = ForeignKey(Publisher, related_name="articles")
> medium = ForeignKey(Medium, related_name="articles")
> text = TextField()
>
> PublisherMediumBilling()
> publisher = ForeignKey(Publisher()
> medium = ForeignKey(Article)
> lots_of_other_columns
> ...
> class Meta:
> unique_together = ['publisher', 'medium']
>
>
>
> I am looking to query all Article from a given publisher, and also fetch
> the related PublisherMediumBilling joining on the columns Publisher and
> Medium,
> Prefetch() object doesn't seem to quite work for this case.
>
> I can of course filter-query for all PublisherMediumBilling and cache it
> and do a in-memory Python JOIN. Is there a way to do through one of the ORM
> Apis ?
>
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