mirror of https://github.com/django/django.git
101 lines
3.1 KiB
Python
101 lines
3.1 KiB
Python
from django.db import models
|
|
from django.db.models.fields.related import (
|
|
ForeignObjectRel, ReverseManyToOneDescriptor,
|
|
)
|
|
from django.db.models.lookups import StartsWith
|
|
from django.db.models.query_utils import PathInfo
|
|
from django.utils.encoding import python_2_unicode_compatible
|
|
|
|
|
|
class CustomForeignObjectRel(ForeignObjectRel):
|
|
"""
|
|
Define some extra Field methods so this Rel acts more like a Field, which
|
|
lets us use ReverseManyToOneDescriptor in both directions.
|
|
"""
|
|
@property
|
|
def foreign_related_fields(self):
|
|
return tuple(lhs_field for lhs_field, rhs_field in self.field.related_fields)
|
|
|
|
def get_attname(self):
|
|
return self.name
|
|
|
|
|
|
class StartsWithRelation(models.ForeignObject):
|
|
"""
|
|
A ForeignObject that uses StartsWith operator in its joins instead of
|
|
the default equality operator. This is logically a many-to-many relation
|
|
and creates a ReverseManyToOneDescriptor in both directions.
|
|
"""
|
|
auto_created = False
|
|
|
|
many_to_many = False
|
|
many_to_one = True
|
|
one_to_many = False
|
|
one_to_one = False
|
|
|
|
rel_class = CustomForeignObjectRel
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
kwargs['on_delete'] = models.DO_NOTHING
|
|
super(StartsWithRelation, self).__init__(*args, **kwargs)
|
|
|
|
@property
|
|
def field(self):
|
|
"""
|
|
Makes ReverseManyToOneDescriptor work in both directions.
|
|
"""
|
|
return self.remote_field
|
|
|
|
def get_extra_restriction(self, where_class, alias, related_alias):
|
|
to_field = self.remote_field.model._meta.get_field(self.to_fields[0])
|
|
from_field = self.model._meta.get_field(self.from_fields[0])
|
|
return StartsWith(to_field.get_col(alias), from_field.get_col(related_alias))
|
|
|
|
def get_joining_columns(self, reverse_join=False):
|
|
return tuple()
|
|
|
|
def get_path_info(self):
|
|
to_opts = self.remote_field.model._meta
|
|
from_opts = self.model._meta
|
|
return [PathInfo(from_opts, to_opts, (to_opts.pk,), self, False, False)]
|
|
|
|
def get_reverse_path_info(self):
|
|
to_opts = self.model._meta
|
|
from_opts = self.remote_field.model._meta
|
|
return [PathInfo(from_opts, to_opts, (to_opts.pk,), self.remote_field, False, False)]
|
|
|
|
def contribute_to_class(self, cls, name, virtual_only=False):
|
|
super(StartsWithRelation, self).contribute_to_class(cls, name, virtual_only)
|
|
setattr(cls, self.name, ReverseManyToOneDescriptor(self))
|
|
|
|
|
|
class BrokenContainsRelation(StartsWithRelation):
|
|
"""
|
|
This model is designed to yield no join conditions and
|
|
raise an exception in ``Join.as_sql()``.
|
|
"""
|
|
def get_extra_restriction(self, where_class, alias, related_alias):
|
|
return None
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class SlugPage(models.Model):
|
|
slug = models.CharField(max_length=20)
|
|
descendants = StartsWithRelation(
|
|
'self',
|
|
from_fields=['slug'],
|
|
to_fields=['slug'],
|
|
related_name='ascendants',
|
|
)
|
|
containers = BrokenContainsRelation(
|
|
'self',
|
|
from_fields=['slug'],
|
|
to_fields=['slug'],
|
|
)
|
|
|
|
class Meta:
|
|
ordering = ['slug']
|
|
|
|
def __str__(self):
|
|
return 'SlugPage %s' % self.slug
|