+class TreeManager(models.Manager):
+ use_for_related_fields = True
+
+ def get_with_path(self, path, root=None, absolute_result=True, pathsep='/', field='slug'):
+ """
+ Returns the object with the path, unless absolute_result is set to False, in which
+ case it returns a tuple containing the deepest object found along the path, and the
+ remainder of the path after that object as a string (or None if there is no remaining
+ path). Raises a DoesNotExist exception if no object is found with the given path.
+
+ If the path you're searching for is known to exist, it is always faster to use
+ absolute_result=True - unless the path depth is over ~40, in which case the high cost
+ of the absolute query makes a binary search (i.e. non-absolute) faster.
+ """
+ # Note: SQLite allows max of 64 tables in one join. That means the binary search will
+ # only work on paths with a max depth of 127 and the absolute fetch will only work
+ # to a max depth of (surprise!) 63. Although this could be handled, chances are your
+ # tree structure won't be that deep.
+ segments = path.split(pathsep)
+
+ # Clean out blank segments. Handles multiple consecutive pathseps.
+ while True:
+ try:
+ segments.remove('')
+ except ValueError:
+ break
+
+ # Special-case a lack of segments. No queries necessary.
+ if not segments:
+ if root is not None:
+ if absolute_result:
+ return root
+ return root, None
+ else:
+ raise self.model.DoesNotExist('%s matching query does not exist.' % self.model._meta.object_name)
+
+ def make_query_kwargs(segments, root):
+ kwargs = {}
+ prefix = ""
+ revsegs = list(segments)
+ revsegs.reverse()
+
+ for segment in revsegs:
+ kwargs["%s%s__exact" % (prefix, field)] = segment
+ prefix += "parent__"
+
+ if prefix:
+ kwargs[prefix[:-2]] = root
+
+ return kwargs
+
+ def find_obj(segments, depth, deepest_found=None):
+ if deepest_found is None:
+ deepest_level = 0
+ elif root is None:
+ deepest_level = deepest_found.get_level() + 1
+ else:
+ deepest_level = deepest_found.get_level() - root.get_level()
+ try:
+ obj = self.get(**make_query_kwargs(segments[deepest_level:depth], deepest_found or root))
+ except self.model.DoesNotExist:
+ if not deepest_level and depth > 1:
+ # make sure there's a root node...
+ depth = 1
+ else:
+ # Try finding one with half the path since the deepest find.
+ depth = (deepest_level + depth)/2
+
+ if deepest_level == depth:
+ # This should happen if nothing is found with any part of the given path.
+ if root is not None and deepest_found is None:
+ return root, pathsep.join(segments)
+ raise
+
+ return find_obj(segments, depth, deepest_found)
+ else:
+ # Yay! Found one!
+ if root is None:
+ deepest_level = obj.get_level() + 1
+ else:
+ deepest_level = obj.get_level() - root.get_level()
+
+ # Could there be a deeper one?
+ if obj.is_leaf_node():
+ return obj, pathsep.join(segments[deepest_level:]) or None
+
+ depth += (len(segments) - depth)/2 or len(segments) - depth
+
+ if depth > deepest_level + obj.get_descendant_count():
+ depth = deepest_level + obj.get_descendant_count()
+
+ if deepest_level == depth:
+ return obj, pathsep.join(segments[deepest_level:]) or None
+
+ try:
+ return find_obj(segments, depth, obj)
+ except self.model.DoesNotExist:
+ # Then this was the deepest.
+ return obj, pathsep.join(segments[deepest_level:])
+
+ if absolute_result:
+ return self.get(**make_query_kwargs(segments, root))
+
+ # Try a modified binary search algorithm. Feed the root in so that query complexity
+ # can be reduced. It might be possible to weight the search towards the beginning
+ # of the path, since short paths are more likely, but how far forward? It would
+ # need to shift depending on len(segments) - perhaps logarithmically?
+ return find_obj(segments, len(segments)/2 or len(segments))
+
+
+class TreeModel(MPTTModel):
+ objects = TreeManager()
+ parent = models.ForeignKey('self', related_name='children', null=True, blank=True)
+ slug = models.SlugField(max_length=255)
+
+ def get_path(self, root=None, pathsep='/', field='slug'):
+ if root == self:
+ return ''
+
+ if root is not None and not self.is_descendant_of(root):
+ raise AncestorDoesNotExist(root)
+
+ qs = self.get_ancestors(include_self=True)
+
+ if root is not None:
+ qs = qs.filter(**{'%s__gt' % self._mptt_meta.level_attr: root.get_level()})
+
+ return pathsep.join([getattr(parent, field, '?') for parent in qs])
+ path = property(get_path)
git.ithinksw.org / philo.git / blobdiff