def mptt_build_tree(queryset, children_key):
'''
:param queryset: the entire tree, or portion of tree, you're trying to construct
:param children_key: key to store children, can't be a field name that's already on the model
:return: QuerySet, with children (also QuerySets) properly nested to each level present
'''
nodes = OrderedDict()
nodes_children = OrderedDict()
for row in queryset:
nodes[row.id] = row
if nodes_children.get(row.parent_id):
nodes_children[row.parent_id]._result_cache.append(row)
else:
nodes_children[row.parent_id] = QuerySet()
nodes_children[row.parent_id]._result_cache = [row]
for k, node in nodes.iteritems():
# Try to find the parent so we can attach the child nodes
setattr(node, children_key, QuerySet())
children = getattr(node, children_key)
children._result_cache = []
if nodes.get(node.parent_id):
children = getattr(nodes[node.parent_id], children_key)
children._result_cache.append(node)
# Build out root nodes for the base level of the list
root_nodes = QuerySet()
root_nodes._result_cache = []
for node_id, node in nodes.iteritems():
if node.parent_id is None:
root_nodes._result_cache.append(node)
return root_nodes
