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196 lines
4.2 KiB
196 lines
4.2 KiB
""" |
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28. Many-to-many relationships between the same two tables |
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In this example, a ``Person`` can have many friends, who are also ``Person`` |
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objects. Friendship is a symmetrical relationship - if I am your friend, you |
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are my friend. Here, ``friends`` is an example of a symmetrical |
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``ManyToManyField``. |
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A ``Person`` can also have many idols - but while I may idolize you, you may |
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not think the same of me. Here, ``idols`` is an example of a non-symmetrical |
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``ManyToManyField``. Only recursive ``ManyToManyField`` fields may be |
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non-symmetrical, and they are symmetrical by default. |
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This test validates that the many-to-many table is created using a mangled name |
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if there is a name clash, and tests that symmetry is preserved where |
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appropriate. |
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""" |
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from django.db import models |
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class Person(models.Model): |
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name = models.CharField(max_length=20) |
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friends = models.ManyToManyField('self') |
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idols = models.ManyToManyField('self', symmetrical=False, related_name='stalkers') |
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def __unicode__(self): |
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return self.name |
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__test__ = {'API_TESTS':""" |
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>>> a = Person(name='Anne') |
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>>> a.save() |
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>>> b = Person(name='Bill') |
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>>> b.save() |
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>>> c = Person(name='Chuck') |
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>>> c.save() |
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>>> d = Person(name='David') |
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>>> d.save() |
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# Add some friends in the direction of field definition |
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# Anne is friends with Bill and Chuck |
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>>> a.friends.add(b,c) |
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# David is friends with Anne and Chuck - add in reverse direction |
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>>> d.friends.add(a,c) |
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# Who is friends with Anne? |
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>>> a.friends.all() |
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[<Person: Bill>, <Person: Chuck>, <Person: David>] |
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# Who is friends with Bill? |
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>>> b.friends.all() |
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[<Person: Anne>] |
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# Who is friends with Chuck? |
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>>> c.friends.all() |
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[<Person: Anne>, <Person: David>] |
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# Who is friends with David? |
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>>> d.friends.all() |
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[<Person: Anne>, <Person: Chuck>] |
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# Bill is already friends with Anne - add Anne again, but in the reverse direction |
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>>> b.friends.add(a) |
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# Who is friends with Anne? |
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>>> a.friends.all() |
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[<Person: Bill>, <Person: Chuck>, <Person: David>] |
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# Who is friends with Bill? |
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>>> b.friends.all() |
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[<Person: Anne>] |
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# Remove Anne from Bill's friends |
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>>> b.friends.remove(a) |
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# Who is friends with Anne? |
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>>> a.friends.all() |
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[<Person: Chuck>, <Person: David>] |
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# Who is friends with Bill? |
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>>> b.friends.all() |
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[] |
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# Clear Anne's group of friends |
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>>> a.friends.clear() |
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# Who is friends with Anne? |
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>>> a.friends.all() |
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[] |
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# Reverse relationships should also be gone |
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# Who is friends with Chuck? |
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>>> c.friends.all() |
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[<Person: David>] |
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# Who is friends with David? |
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>>> d.friends.all() |
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[<Person: Chuck>] |
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# Add some idols in the direction of field definition |
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# Anne idolizes Bill and Chuck |
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>>> a.idols.add(b,c) |
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# Bill idolizes Anne right back |
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>>> b.idols.add(a) |
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# David is idolized by Anne and Chuck - add in reverse direction |
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>>> d.stalkers.add(a,c) |
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# Who are Anne's idols? |
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>>> a.idols.all() |
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[<Person: Bill>, <Person: Chuck>, <Person: David>] |
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# Who is stalking Anne? |
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>>> a.stalkers.all() |
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[<Person: Bill>] |
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# Who are Bill's idols? |
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>>> b.idols.all() |
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[<Person: Anne>] |
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# Who is stalking Bill? |
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>>> b.stalkers.all() |
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[<Person: Anne>] |
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# Who are Chuck's idols? |
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>>> c.idols.all() |
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[<Person: David>] |
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# Who is stalking Chuck? |
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>>> c.stalkers.all() |
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[<Person: Anne>] |
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# Who are David's idols? |
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>>> d.idols.all() |
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[] |
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# Who is stalking David |
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>>> d.stalkers.all() |
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[<Person: Anne>, <Person: Chuck>] |
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# Bill is already being stalked by Anne - add Anne again, but in the reverse direction |
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>>> b.stalkers.add(a) |
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# Who are Anne's idols? |
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>>> a.idols.all() |
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[<Person: Bill>, <Person: Chuck>, <Person: David>] |
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# Who is stalking Anne? |
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[<Person: Bill>] |
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# Who are Bill's idols |
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>>> b.idols.all() |
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[<Person: Anne>] |
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# Who is stalking Bill? |
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>>> b.stalkers.all() |
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[<Person: Anne>] |
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# Remove Anne from Bill's list of stalkers |
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>>> b.stalkers.remove(a) |
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# Who are Anne's idols? |
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>>> a.idols.all() |
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[<Person: Chuck>, <Person: David>] |
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# Who is stalking Anne? |
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>>> a.stalkers.all() |
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[<Person: Bill>] |
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# Who are Bill's idols? |
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>>> b.idols.all() |
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[<Person: Anne>] |
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# Who is stalking Bill? |
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>>> b.stalkers.all() |
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[] |
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# Clear Anne's group of idols |
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>>> a.idols.clear() |
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# Who are Anne's idols |
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>>> a.idols.all() |
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[] |
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# Reverse relationships should also be gone |
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# Who is stalking Chuck? |
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>>> c.stalkers.all() |
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[] |
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# Who is friends with David? |
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>>> d.stalkers.all() |
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[<Person: Chuck>] |
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"""}
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