75 lines
2.2 KiB
Python
75 lines
2.2 KiB
Python
"""
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Tests for the update() queryset method that allows in-place, multi-object
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updates.
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"""
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from django.db import models
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class DataPoint(models.Model):
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name = models.CharField(max_length=20)
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value = models.CharField(max_length=20)
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another_value = models.CharField(max_length=20, blank=True)
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def __unicode__(self):
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return unicode(self.name)
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class RelatedPoint(models.Model):
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name = models.CharField(max_length=20)
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data = models.ForeignKey(DataPoint)
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def __unicode__(self):
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return unicode(self.name)
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__test__ = {'API_TESTS': """
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>>> DataPoint(name="d0", value="apple").save()
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>>> DataPoint(name="d2", value="banana").save()
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>>> d3 = DataPoint(name="d3", value="banana")
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>>> d3.save()
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>>> RelatedPoint(name="r1", data=d3).save()
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Objects are updated by first filtering the candidates into a queryset and then
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calling the update() method. It executes immediately and returns nothing.
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>>> DataPoint.objects.filter(value="apple").update(name="d1")
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>>> DataPoint.objects.filter(value="apple")
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[<DataPoint: d1>]
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We can update multiple objects at once.
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>>> DataPoint.objects.filter(value="banana").update(value="pineapple")
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>>> DataPoint.objects.get(name="d2").value
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u'pineapple'
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Foreign key fields can also be updated, although you can only update the object
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referred to, not anything inside the related object.
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>>> d = DataPoint.objects.get(name="d1")
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>>> RelatedPoint.objects.filter(name="r1").update(data=d)
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>>> RelatedPoint.objects.filter(data__name="d1")
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[<RelatedPoint: r1>]
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Multiple fields can be updated at once
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>>> DataPoint.objects.filter(value="pineapple").update(value="fruit", another_value="peaches")
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>>> d = DataPoint.objects.get(name="d2")
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>>> d.value, d.another_value
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(u'fruit', u'peaches')
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In the rare case you want to update every instance of a model, update() is also
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a manager method.
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>>> DataPoint.objects.update(value='thing')
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>>> DataPoint.objects.values('value').distinct()
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[{'value': u'thing'}]
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We do not support update on already sliced query sets.
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>>> DataPoint.objects.all()[:2].update(another_value='another thing')
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Traceback (most recent call last):
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...
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AssertionError: Cannot update a query once a slice has been taken.
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"""
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}
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