#29551: My use-case of QuerySet.extra(): Join two models without explicit
relation
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Reporter: Bowser | Owner: nobody
Type: Uncategorized | Status: closed
Component: Uncategorized | Version: 2.0
Severity: Normal | Resolution: invalid
Keywords: QuerySet.extra | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by Simon Charette):
* status: new => closed
* resolution: => invalid
Comment:
Hey Bowser,
I think the best approach here would be to define a
`django.db.models.related.ForeignObject` on your model by making sure to
define appropriate `from_fields` and `to_fields`. Such objects will behave
just like `ForeignKey`s with regards to ORM interactions (`filter`,
`annotate`, `values`, ...) but aren't backed by a implicit concrete
column. Under the hood `ForeignKey` is a subclass of `ForeignKey` that
creates a concrete a column to use it as `from_fields` and defaults
`to_fields` to the referenced model's primary key.
For example on your `Inbox` model.
{{{#!python
class Inbox(models.Model):
...
sender_email = models.EmailField(db_column='SenderEmail')
customer = ForeignObject(Customer, models.CASCADE,
from_fields=['sender_email'], to_fields=['email'])
class Meta:
managed = False
...
}}}
I'll close this ticket as invalid for now but feel free to re-open it if
the provided alternative to your usage of `extra()` isn't appropriate.
--
Ticket URL: <https://code.djangoproject.com/ticket/29551#comment:1>
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