django/tests/modeltests/select_related/models.py

"""
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

# Who remembers high school biology?

class Domain(models.Model):
    name = models.CharField(max_length=50)
    def __unicode__(self):
        return self.name

class Kingdom(models.Model):
    name = models.CharField(max_length=50)
    domain = models.ForeignKey(Domain)
    def __unicode__(self):
        return self.name

class Phylum(models.Model):
    name = models.CharField(max_length=50)
    kingdom = models.ForeignKey(Kingdom)
    def __unicode__(self):
        return self.name

class Klass(models.Model):
    name = models.CharField(max_length=50)
    phylum = models.ForeignKey(Phylum)
    def __unicode__(self):
        return self.name

class Order(models.Model):
    name = models.CharField(max_length=50)
    klass = models.ForeignKey(Klass)
    def __unicode__(self):
        return self.name

class Family(models.Model):
    name = models.CharField(max_length=50)
    order = models.ForeignKey(Order)
    def __unicode__(self):
        return self.name

class Genus(models.Model):
    name = models.CharField(max_length=50)
    family = models.ForeignKey(Family)
    def __unicode__(self):
        return self.name

class Species(models.Model):
    name = models.CharField(max_length=50)
    genus = models.ForeignKey(Genus)
    def __unicode__(self):
        return self.name