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