mirror of https://github.com/django/django.git
193 lines
4.0 KiB
Python
193 lines
4.0 KiB
Python
"""
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27. 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 people. Friendship is a
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symmetrical relationship - if I am your friend, you are my friend.
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A person can also have many idols - but while I may idolize you, you may not think
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the same of me. 'Idols' is an example of a non-symmetrical m2m field. Only recursive
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m2m fields may be non-symmetrical, and they are symmetrical by default.
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This test validates that the m2m table will create a mangled name for the m2m table if
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there will be a clash, and tests that symmetry is preserved where 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(maxlength=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 __str__(self):
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return self.name
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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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