mirror of
https://github.com/django/django.git
synced 2024-11-29 22:56:46 +01:00
97 lines
2.2 KiB
Python
97 lines
2.2 KiB
Python
"""
|
|
41. Tests for select_related()
|
|
|
|
``select_related()`` follows all relationships and pre-caches any foreign key
|
|
values so that complex trees can be fetched in a single query. However, this
|
|
isn't always a good idea, so the ``depth`` argument control how many "levels"
|
|
the select-related behavior will traverse.
|
|
"""
|
|
|
|
from django.db import models
|
|
from django.utils.encoding import python_2_unicode_compatible
|
|
|
|
# Who remembers high school biology?
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Domain(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Kingdom(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
domain = models.ForeignKey(Domain)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Phylum(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
kingdom = models.ForeignKey(Kingdom)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Klass(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
phylum = models.ForeignKey(Phylum)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Order(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
klass = models.ForeignKey(Klass)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Family(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
order = models.ForeignKey(Order)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Genus(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
family = models.ForeignKey(Family)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class Species(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
genus = models.ForeignKey(Genus)
|
|
|
|
def __str__(self):
|
|
return self.name
|
|
|
|
# and we'll invent a new thing so we have a model with two foreign keys
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class HybridSpecies(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
parent_1 = models.ForeignKey(Species, related_name='child_1')
|
|
parent_2 = models.ForeignKey(Species, related_name='child_2')
|
|
|
|
def __str__(self):
|
|
return self.name
|