"""

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.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

from django.contrib.contenttypes.models import ContentType

from django.db import models

# Who remembers high school biology?

class Domain(models.Model):

    name = models.CharField(max_length=50)

class Kingdom(models.Model):

    name = models.CharField(max_length=50)

    domain = models.ForeignKey(Domain, models.CASCADE)

class Phylum(models.Model):

    name = models.CharField(max_length=50)

    kingdom = models.ForeignKey(Kingdom, models.CASCADE)

class Klass(models.Model):

    name = models.CharField(max_length=50)

    phylum = models.ForeignKey(Phylum, models.CASCADE)

class Order(models.Model):

    name = models.CharField(max_length=50)

    klass = models.ForeignKey(Klass, models.CASCADE)

class Family(models.Model):

    name = models.CharField(max_length=50)

    order = models.ForeignKey(Order, models.CASCADE)

class Genus(models.Model):

    name = models.CharField(max_length=50)

    family = models.ForeignKey(Family, models.CASCADE)

class Species(models.Model):

    name = models.CharField(max_length=50)

    genus = models.ForeignKey(Genus, models.CASCADE)

# and we'll invent a new thing so we have a model with two foreign keys

class HybridSpecies(models.Model):

    name = models.CharField(max_length=50)

    parent_1 = models.ForeignKey(Species, models.CASCADE, related_name="child_1")

    parent_2 = models.ForeignKey(Species, models.CASCADE, related_name="child_2")

class Topping(models.Model):

    name = models.CharField(max_length=30)

class Pizza(models.Model):

    name = models.CharField(max_length=100)

    toppings = models.ManyToManyField(Topping)

class TaggedItem(models.Model):

    tag = models.CharField(max_length=30)

    content_type = models.ForeignKey(

        ContentType, models.CASCADE, related_name="select_related_tagged_items"

    )

    object_id = models.PositiveIntegerField()

    content_object = GenericForeignKey("content_type", "object_id")

class Bookmark(models.Model):

    url = models.URLField()

    tags = GenericRelation(TaggedItem)