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diff --git a/tests/modeltests/select_related/models.py b/tests/modeltests/select_related/models.py
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+"""
+XXX. 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(maxlength=50)
+    def __str__(self):
+        return self.name
+
+class Kingdom(models.Model):
+    name = models.CharField(maxlength=50)
+    domain = models.ForeignKey(Domain)
+    def __str__(self):
+        return self.name
+
+class Phylum(models.Model):
+    name = models.CharField(maxlength=50)
+    kingdom = models.ForeignKey(Kingdom)
+    def __str__(self):
+        return self.name
+    
+class Klass(models.Model):
+    name = models.CharField(maxlength=50)
+    phylum = models.ForeignKey(Phylum)
+    def __str__(self):
+        return self.name
+    
+class Order(models.Model):
+    name = models.CharField(maxlength=50)
+    klass = models.ForeignKey(Klass)
+    def __str__(self):
+        return self.name
+
+class Family(models.Model):
+    name = models.CharField(maxlength=50)
+    order = models.ForeignKey(Order)
+    def __str__(self):
+        return self.name
+
+class Genus(models.Model):
+    name = models.CharField(maxlength=50)
+    family = models.ForeignKey(Family)
+    def __str__(self):
+        return self.name
+
+class Species(models.Model):
+    name = models.CharField(maxlength=50)
+    genus = models.ForeignKey(Genus)
+    def __str__(self):
+        return self.name
+
+def create_tree(stringtree):
+    """Helper to create a complete tree"""
+    names = stringtree.split()
+    models = [Domain, Kingdom, Phylum, Klass, Order, Family, Genus, Species]
+    assert len(names) == len(models), (names, models)
+    
+    parent = None
+    for name, model in zip(names, models):
+        try:
+            obj = model.objects.get(name=name)
+        except model.DoesNotExist:
+            obj = model(name=name)
+        if parent:
+            setattr(obj, parent.__class__.__name__.lower(), parent)
+        obj.save()
+        parent = obj
+
+__test__ = {'API_TESTS':"""
+
+# Set up.
+# The test runner sets settings.DEBUG to False, but we want to gather queries
+# so we'll set it to True here and reset it at the end of the test suite.
+>>> from django.conf import settings
+>>> settings.DEBUG = True
+
+>>> create_tree("Eukaryota Animalia Anthropoda Insecta Diptera Drosophilidae Drosophila melanogaster")
+>>> create_tree("Eukaryota Animalia Chordata Mammalia Primates Hominidae Homo sapiens")
+>>> create_tree("Eukaryota Plantae Magnoliophyta Magnoliopsida Fabales Fabaceae Pisum sativum")
+>>> create_tree("Eukaryota Fungi Basidiomycota Homobasidiomycatae Agaricales Amanitacae Amanita muscaria")
+
+>>> from django import db
+
+# Normally, accessing FKs doesn't fill in related objects:
+>>> db.reset_queries()
+>>> fly = Species.objects.get(name="melanogaster")
+>>> fly.genus.family.order.klass.phylum.kingdom.domain
+<Domain: Eukaryota>
+>>> len(db.connection.queries)
+8
+
+# However, a select_related() call will fill in those related objects without any extra queries:
+>>> db.reset_queries()
+>>> person = Species.objects.select_related().get(name="sapiens")
+>>> person.genus.family.order.klass.phylum.kingdom.domain
+<Domain: Eukaryota>
+>>> len(db.connection.queries)
+1
+
+# select_related() also of course applies to entire lists, not just items.
+# Without select_related()
+>>> db.reset_queries()
+>>> world = Species.objects.all()
+>>> [o.genus.family for o in world]
+[<Family: Drosophilidae>, <Family: Hominidae>, <Family: Fabaceae>, <Family: Amanitacae>]
+>>> len(db.connection.queries)
+9
+
+# With select_related():
+>>> db.reset_queries()
+>>> world = Species.objects.all().select_related()
+>>> [o.genus.family for o in world]
+[<Family: Drosophilidae>, <Family: Hominidae>, <Family: Fabaceae>, <Family: Amanitacae>]
+>>> len(db.connection.queries)
+1
+
+# The "depth" argument to select_related() will stop the descent at a particular level:
+>>> db.reset_queries()
+>>> pea = Species.objects.select_related(depth=1).get(name="sativum")
+>>> pea.genus.family.order.klass.phylum.kingdom.domain
+<Domain: Eukaryota>
+
+# Notice: one few query than above because of depth=1
+>>> len(db.connection.queries)
+7
+
+>>> db.reset_queries()
+>>> pea = Species.objects.select_related(depth=5).get(name="sativum")
+>>> pea.genus.family.order.klass.phylum.kingdom.domain
+<Domain: Eukaryota>
+>>> len(db.connection.queries)
+3
+
+>>> db.reset_queries()
+>>> world = Species.objects.all().select_related(depth=2)
+>>> [o.genus.family.order for o in world]
+[<Order: Diptera>, <Order: Primates>, <Order: Fabales>, <Order: Agaricales>]
+>>> len(db.connection.queries)
+5
+
+# Reset DEBUG to where we found it.
+>>> settings.DEBUG = False
+"""}