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djangodjango-mptt
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Reputation: 65

Django-mptt TreeManyToManyField not working?

I try for a little while set up django-mptt in my project. I took a sample from tutorial and changed model acordingly which looks like this:

class Genre(MPTTModel):
pk = models.AutoField(primary_key=True)
name = models.CharField(max_length=50, unique=True)
parent = TreeManyToManyField('self', null=True, blank=True, related_name='children')

class MPTTMeta:
    order_insertion_by = ['name']

Unfortunately console prints out something like this:

/srv/tokedu/local/lib/python2.7/site-packages/Django-1.3.1-py2.7.egg/django/db/models/base.pyc in _set_pk_val(self, value)
    426 
    427     def _set_pk_val(self, value):
--> 428         return setattr(self, self._meta.pk.attname, value)
    429 
    430     pk = property(_get_pk_val, _set_pk_val)
/srv/tokedu/local/lib/python2.7/site-packages/Django-1.3.1-py2.7.egg/django/db/models/base.pyc in _set_pk_val(self, value)
    426 
    427     def _set_pk_val(self, value):
--> 428         return setattr(self, self._meta.pk.attname, value)
    429 
    430     pk = property(_get_pk_val, _set_pk_val)
RuntimeError: maximum recursion depth exceeded

I think django-mptt just not support TreeManyToManyField. Anyone had the same problem??

Upvotes: 3

Views: 1528

Answers (1)

craigds
craigds

Reputation: 2157

Nodes can't have more than one parent. That fundamentally changes your data structure - it's no longer a tree, it's an arbitrary graph.

django-mptt only handles trees. If you have a large graph database, you've got a very different problem. You might want to look into using a graph database rather than an RDBMS.

AFAIK there's no django apps which make graph structures easy, but then again I've never really needed to :)

Useful links:

Upvotes: 4

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