#22158: Allow model level custom lookups
-------------------------------------+-------------------------------------
Reporter: akaariai | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by akaariai):
I came up with another instance where this feature would be useful for one
of my projects, and decided it might be time to move forward with this.
The syntax I came up with was:
{{{
class User(models.Model):
valid_from = models.DateField()
valid_until = models.DateField(null=True, blank=True)
def is_active_at(self, dt):
return (self.valid_from < dt and
(self.valid_until is None or self.valid_until > dt))
@models.lookup
def is_active_at(cls, dt):
return (Q(valid_from__lt=dt) &
(Q(valid_until__gt=dt) | Q(valid_until__isnull=True)))
@property
def valid_from_year(self):
return self.valid_from.year
@models.lookup
def valid_from_year(cls):
return Extract(F('valid_from'), 'year')
}}}
So, the idea is that you could do both:
{{{
User.objects.filter(is_valid_at=now())
}}}
and
{{{
user.is_valid_at(now())
}}}
Similarly you could do both:
{{{
User.objects.filter(valid_from_year__lte=2000)
}}}
and
{{{
user.valid_from_year <= 2000
}}}
The idea would be that we use some decorators to mark methods for database
lookups and expressions. When the transform/expression is referenced by
the ORM, we first call the decorated method, then we resolve the
expression. It might be worth it to pass the query to the methods, too.
Does this seem like an OK API?
--
Ticket URL: <https://code.djangoproject.com/ticket/22158#comment:3>
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