/
ns_tree.py
728 lines (604 loc) · 23.7 KB
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ns_tree.py
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# -*- coding: utf-8 -*-
"""
treebeard.ns_tree
-----------------
Nested Sets Tree.
:copyright: 2008-2010 by Gustavo Picon
:license: Apache License 2.0
An implementation of Nested Sets trees for Django 1.0+, as described by
`Joe Celko`_ in `Trees and Hierarchies in SQL for Smarties`_.
Nested sets have very efficient reads at the cost of high maintenance on
write/delete operations.
.. _`Joe Celko`: http://www.celko.com/
.. _`Trees and Hierarchies in SQL for Smarties`:
http://www.elsevier.com/wps/find/bookdescription.cws_home/702605/description
"""
import operator
from django.db.models import Q
from django.core import serializers
from django.db import models, transaction, connection
from treebeard.models import Node
from treebeard.exceptions import InvalidMoveToDescendant, PathOverflow
class NS_NodeQuerySet(models.query.QuerySet):
"""
Custom queryset for the tree node manager.
Needed only for the customized delete method.
"""
def delete(self, removed_ranges=None):
"""
Custom delete method, will remove all descendant nodes to ensure a
consistent tree (no orphans)
:returns: ``None``
"""
if removed_ranges is not None:
# we already know the children, let's call the default django
# delete method and let it handle the removal of the user's
# foreign keys...
super(NS_NodeQuerySet, self).delete()
cursor = connection.cursor()
# Now closing the gap (Celko's trees book, page 62)
# We do this for every gap that was left in the tree when the nodes
# were removed. If many nodes were removed, we're going to update
# the same nodes over and over again. This would be probably
# cheaper precalculating the gapsize per intervals, or just do a
# complete reordering of the tree (uses COUNT)...
for tree_id, drop_lft, drop_rgt in sorted(removed_ranges,
reverse=True):
sql, params = self.model._get_close_gap_sql(drop_lft, drop_rgt,
tree_id)
cursor.execute(sql, params)
else:
# we'll have to manually run through all the nodes that are going
# to be deleted and remove nodes from the list if an ancestor is
# already getting removed, since that would be redundant
removed = {}
for node in self.order_by('tree_id', 'lft'):
found = False
for rid, rnode in removed.items():
if node.is_descendant_of(rnode):
found = True
break
if not found:
removed[node.id] = node
# ok, got the minimal list of nodes to remove...
# we must also remove their descendants
toremove = []
ranges = []
for id, node in removed.items():
toremove.append(
Q(lft__range=(node.lft, node.rgt))&Q(tree_id=node.tree_id))
ranges.append((node.tree_id, node.lft, node.rgt))
if toremove:
self.model.objects.filter(
reduce(operator.or_, toremove)).delete(
removed_ranges=ranges)
transaction.commit_unless_managed()
class NS_NodeManager(models.Manager):
""" Custom manager for nodes.
"""
def get_query_set(self):
"""
Sets the custom queryset as the default.
"""
return NS_NodeQuerySet(self.model).order_by('tree_id', 'lft')
class NS_Node(Node):
"""
Abstract model to create your own Nested Sets Trees.
.. attribute:: node_order_by
Attribute: a list of model fields that will be used for node
ordering. When enabled, all tree operations will assume this ordering.
Example::
node_order_by = ['field1', 'field2', 'field3']
.. attribute:: depth
``PositiveIntegerField``, depth of a node in the tree. A root node
has a depth of *1*.
.. attribute:: lft
``PositiveIntegerField``
.. attribute:: rgt
``PositiveIntegerField``
.. attribute:: tree_id
``PositiveIntegerField``
"""
node_order_by = []
lft = models.PositiveIntegerField(db_index=True)
rgt = models.PositiveIntegerField(db_index=True)
tree_id = models.PositiveIntegerField(db_index=True)
depth = models.PositiveIntegerField(db_index=True)
objects = NS_NodeManager()
@classmethod
def add_root(cls, **kwargs):
"""
Adds a root node to the tree.
See: :meth:`treebeard.Node.add_root`
"""
# do we have a root node already?
last_root = cls.get_last_root_node()
if last_root and last_root.node_order_by:
# there are root nodes and node_order_by has been set
# delegate sorted insertion to add_sibling
return last_root.add_sibling('sorted-sibling', **kwargs)
if last_root:
# adding the new root node as the last one
#newtree_id = last_root.tree_id + 100
newtree_id = last_root.tree_id + 1
else:
# adding the first root node
#newtree_id = 100
newtree_id = 1
# creating the new object
newobj = cls(**kwargs)
newobj.depth = 1
newobj.tree_id = newtree_id
newobj.lft = 1
#newobj.rgt = 400000000
newobj.rgt = 2
# saving the instance before returning it
newobj.save()
transaction.commit_unless_managed()
return newobj
@classmethod
def _move_right(cls, tree_id, rgt, lftmove=False, incdec=2):
if lftmove:
lftop = '>='
else:
lftop = '>'
sql = 'UPDATE %(table)s ' \
' SET lft = CASE WHEN lft %(lftop)s %(parent_rgt)d ' \
' THEN lft %(incdec)+d ' \
' ELSE lft END, ' \
' rgt = CASE WHEN rgt >= %(parent_rgt)d ' \
' THEN rgt %(incdec)+d ' \
' ELSE rgt END ' \
' WHERE rgt >= %(parent_rgt)d AND ' \
' tree_id = %(tree_id)s' % {
'table': connection.ops.quote_name(cls._meta.db_table),
'parent_rgt': rgt,
'tree_id': tree_id,
'lftop': lftop,
'incdec': incdec}
return sql, []
@classmethod
def _move_tree_right(cls, tree_id):
sql = 'UPDATE %(table)s ' \
' SET tree_id = tree_id+1 ' \
' WHERE tree_id >= %(tree_id)d' % {
'table': connection.ops.quote_name(cls._meta.db_table),
'tree_id': tree_id}
return sql, []
def add_child(self, **kwargs):
"""
Adds a child to the node.
See: :meth:`treebeard.Node.add_child`
"""
if not self.is_leaf():
# there are child nodes, delegate insertion to add_sibling
if self.node_order_by:
pos = 'sorted-sibling'
else:
pos = 'last-sibling'
last_child = self.get_last_child()
tmp = self.__class__.objects.get(pk=self.id)
last_child._cached_parent_obj = self
return last_child.add_sibling(pos, **kwargs)
# we're adding the first child of this node
sql, params = self.__class__._move_right(self.tree_id, self.rgt, False,
2)
# creating a new object
newobj = self.__class__(**kwargs)
newobj.tree_id = self.tree_id
newobj.depth = self.depth + 1
newobj.lft = self.lft+1
newobj.rgt = self.lft+2
# this is just to update the cache
self.rgt = self.rgt+2
newobj._cached_parent_obj = self
cursor = connection.cursor()
cursor.execute(sql, params)
# saving the instance before returning it
newobj.save()
transaction.commit_unless_managed()
return newobj
def add_sibling(self, pos=None, **kwargs):
"""
Adds a new node as a sibling to the current node object.
See: :meth:`treebeard.Node.add_sibling`
"""
pos = self._fix_add_sibling_opts(pos)
# creating a new object
newobj = self.__class__(**kwargs)
newobj.depth = self.depth
sql = None
target = self
if target.is_root():
newobj.lft = 1
newobj.rgt = 2
if pos == 'sorted-sibling':
siblings = list(target.get_sorted_pos_queryset(
target.get_siblings(), newobj))
if siblings:
pos = 'left'
target = siblings[0]
else:
pos = 'last-sibling'
last_root = target.__class__.get_last_root_node()
if pos == 'last-sibling' \
or (pos == 'right' and target == last_root):
newobj.tree_id = last_root.tree_id + 1
else:
newpos = {'first-sibling': 1,
'left': target.tree_id,
'right': target.tree_id + 1}[pos]
sql, params = target.__class__._move_tree_right(newpos)
newobj.tree_id = newpos
else:
newobj.tree_id = target.tree_id
if pos == 'sorted-sibling':
siblings = list(target.get_sorted_pos_queryset(
target.get_siblings(), newobj))
if siblings:
pos = 'left'
target = siblings[0]
else:
pos = 'last-sibling'
if pos in ('left', 'right', 'first-sibling'):
siblings = list(target.get_siblings())
if pos == 'right':
if target == siblings[-1]:
pos = 'last-sibling'
else:
pos = 'left'
found = False
for node in siblings:
if found:
target = node
break
elif node == target:
found = True
if pos == 'left':
if target == siblings[0]:
pos = 'first-sibling'
if pos == 'first-sibling':
target = siblings[0]
move_right = self.__class__._move_right
if pos == 'last-sibling':
newpos = target.get_parent().rgt
sql, params = move_right(target.tree_id, newpos, False, 2)
elif pos == 'first-sibling':
newpos = target.lft
sql, params = move_right(target.tree_id, newpos-1, False, 2)
elif pos == 'left':
newpos = target.lft
sql, params = move_right(target.tree_id, newpos, True, 2)
newobj.lft = newpos
newobj.rgt = newpos + 1
# saving the instance before returning it
if sql:
cursor = connection.cursor()
cursor.execute(sql, params)
newobj.save()
transaction.commit_unless_managed()
return newobj
def move(self, target, pos=None):
"""
Moves the current node and all it's descendants to a new position
relative to another node.
See: :meth:`treebeard.Node.move`
"""
pos = self._fix_move_opts(pos)
cls = self.__class__
stmts = []
parent = None
if pos in ('first-child', 'last-child', 'sorted-child'):
# moving to a child
if target.is_leaf():
parent = target
pos = 'last-child'
else:
target = target.get_last_child()
pos = {'first-child': 'first-sibling',
'last-child': 'last-sibling',
'sorted-child': 'sorted-sibling'}[pos]
if target.is_descendant_of(self):
raise InvalidMoveToDescendant("Can't move node to a descendant.")
if self == target and (
(pos == 'left') or \
(pos in ('right', 'last-sibling') and \
target == target.get_last_sibling()) or \
(pos == 'first-sibling' and \
target == target.get_first_sibling())):
# special cases, not actually moving the node so no need to UPDATE
return
if pos == 'sorted-sibling':
siblings = list(target.get_sorted_pos_queryset(
target.get_siblings(), self))
if siblings:
pos = 'left'
target = siblings[0]
else:
pos = 'last-sibling'
if pos in ('left', 'right', 'first-sibling'):
siblings = list(target.get_siblings())
if pos == 'right':
if target == siblings[-1]:
pos = 'last-sibling'
else:
pos = 'left'
found = False
for node in siblings:
if found:
target = node
break
elif node == target:
found = True
if pos == 'left':
if target == siblings[0]:
pos = 'first-sibling'
if pos == 'first-sibling':
target = siblings[0]
# ok let's move this
cursor = connection.cursor()
move_right = cls._move_right
gap = self.rgt - self.lft + 1
sql = None
target_tree = target.tree_id
# first make a hole
if pos == 'last-child':
newpos = parent.rgt
sql, params = move_right(target.tree_id, newpos, False, gap)
elif target.is_root():
newpos = 1
if pos == 'last-sibling':
target_tree = target.get_siblings().reverse()[0].tree_id + 1
elif pos == 'first-sibling':
target_tree = 1
sql, params = cls._move_tree_right(1)
elif pos == 'left':
sql, params = cls._move_tree_right(target.tree_id)
else:
if pos == 'last-sibling':
newpos = target.get_parent().rgt
sql, params = move_right(target.tree_id, newpos, False, gap)
elif pos == 'first-sibling':
newpos = target.lft
sql, params = move_right(target.tree_id, newpos-1, False, gap)
elif pos == 'left':
newpos = target.lft
sql, params = move_right(target.tree_id, newpos, True, gap)
if sql:
cursor.execute(sql, params)
# we reload 'self' because lft/rgt may have changed
fromobj = cls.objects.get(pk=self.id)
depthdiff = target.depth - fromobj.depth
if parent:
depthdiff += 1
# move the tree to the hole
sql = "UPDATE %(table)s " \
" SET tree_id = %(target_tree)d, " \
" lft = lft + %(jump)d , " \
" rgt = rgt + %(jump)d , " \
" depth = depth + %(depthdiff)d " \
" WHERE tree_id = %(from_tree)d AND " \
" lft BETWEEN %(fromlft)d AND %(fromrgt)d" % {
'table': connection.ops.quote_name(cls._meta.db_table),
'from_tree': fromobj.tree_id,
'target_tree': target_tree,
'jump': newpos - fromobj.lft,
'depthdiff': depthdiff,
'fromlft': fromobj.lft,
'fromrgt': fromobj.rgt}
cursor.execute(sql, [])
# close the gap
sql, params = cls._get_close_gap_sql(fromobj.lft,
fromobj.rgt, fromobj.tree_id)
cursor.execute(sql, params)
transaction.commit_unless_managed()
@classmethod
def _get_close_gap_sql(cls, drop_lft, drop_rgt, tree_id):
sql = 'UPDATE %(table)s ' \
' SET lft = CASE ' \
' WHEN lft > %(drop_lft)d ' \
' THEN lft - %(gapsize)d ' \
' ELSE lft END, ' \
' rgt = CASE ' \
' WHEN rgt > %(drop_lft)d ' \
' THEN rgt - %(gapsize)d ' \
' ELSE rgt END ' \
' WHERE (lft > %(drop_lft)d ' \
' OR rgt > %(drop_lft)d) AND '\
' tree_id=%(tree_id)d' % {
'table': connection.ops.quote_name(cls._meta.db_table),
'gapsize': drop_rgt - drop_lft + 1,
'drop_lft': drop_lft,
'tree_id': tree_id}
return sql, []
@classmethod
def load_bulk(cls, bulk_data, parent=None, keep_ids=False):
"""
Loads a list/dictionary structure to the tree.
See: :meth:`treebeard.Node.move`
"""
# tree, iterative preorder
added = []
if parent:
parent_id = parent.id
else:
parent_id = None
# stack of nodes to analize
stack = [(parent_id, node) for node in bulk_data[::-1]]
while stack:
parent_id, node_struct = stack.pop()
# shallow copy of the data strucure so it doesn't persist...
node_data = node_struct['data'].copy()
if keep_ids:
node_data['id'] = node_struct['id']
if parent_id:
parent = cls.objects.get(pk=parent_id)
node_obj = parent.add_child(**node_data)
else:
node_obj = cls.add_root(**node_data)
added.append(node_obj.id)
if 'children' in node_struct:
# extending the stack with the current node as the parent of
# the new nodes
stack.extend([(node_obj.id, node) \
for node in node_struct['children'][::-1]])
transaction.commit_unless_managed()
return added
def get_children(self):
"""
:returns: A queryset of all the node's children
See: :meth:`treebeard.Node.get_children`
"""
return self.get_descendants().filter(depth=self.depth+1)
def get_depth(self):
"""
:returns: the depth (level) of the node
See: :meth:`treebeard.Node.get_depth`
"""
return self.depth
def is_leaf(self):
"""
:returns: True if the node is a leaf node (else, returns False)
See: :meth:`treebeard.Node.is_leaf`
"""
return self.rgt - self.lft == 1
def get_root(self):
"""
:returns: the root node for the current node object.
See: :meth:`treebeard.Node.get_root`
"""
if self.lft == 1:
return self
return self.__class__.objects.get(tree_id=self.tree_id,
lft=1)
def get_siblings(self):
"""
:returns: A queryset of all the node's siblings, including the node
itself.
See: :meth:`treebeard.Node.get_siblings`
"""
if self.lft == 1:
return self.get_root_nodes()
return self.get_parent(True).get_children()
@classmethod
def dump_bulk(cls, parent=None, keep_ids=True):
"""
Dumps a tree branch to a python data structure.
See: :meth:`treebeard.Node.dump_bulk`
"""
qset = cls.get_tree(parent)
ret, lnk = [], {}
for pyobj in qset:
serobj = serializers.serialize('python', [pyobj])[0]
# for serobj in serializers.serialize('python', qset):
# django's serializer stores the attributes in 'fields'
fields = serobj['fields']
depth = fields['depth']
lft = fields['lft']
tree_id = fields['tree_id']
# this will be useless in load_bulk
del fields['lft']
del fields['rgt']
del fields['depth']
del fields['tree_id']
if 'id' in fields:
# this happens immediately after a load_bulk
del fields['id']
newobj = {'data': fields}
if keep_ids:
newobj['id'] = serobj['pk']
if (not parent and depth == 1) or \
(parent and depth == parent.depth):
ret.append(newobj)
else:
parentobj = pyobj.get_parent()
parentser = lnk[parentobj.id]
if 'children' not in parentser:
parentser['children'] = []
parentser['children'].append(newobj)
lnk[pyobj.id] = newobj
return ret
@classmethod
def get_tree(cls, parent=None):
"""
:returns: A *queryset* of nodes ordered as DFS, including the parent.
If no parent is given, all trees are returned.
See: :meth:`treebeard.Node.get_tree`
.. note::
This metod returns a queryset.
"""
if parent is None:
# return the entire tree
return cls.objects.all()
if parent.is_leaf():
return cls.objects.filter(pk=parent.id)
return cls.objects.filter(
tree_id=parent.tree_id,
lft__range=(parent.lft, parent.rgt-1))
def get_descendants(self):
"""
:returns: A queryset of all the node's descendants as DFS, doesn't
include the node itself
See: :meth:`treebeard.Node.get_descendants`
"""
if self.is_leaf():
return self.__class__.objects.none()
return self.__class__.get_tree(self).exclude(pk=self.id)
def get_descendant_count(self):
"""
:returns: the number of descendants of a node.
See: :meth:`treebeard.Node.get_descendant_count`
"""
return (self.rgt - self.lft - 1) / 2
def get_ancestors(self):
"""
:returns: A queryset containing the current node object's ancestors,
starting by the root node and descending to the parent.
See: :meth:`treebeard.Node.get_ancestors`
"""
if self.is_root():
return self.__class__.objects.none()
return self.__class__.objects.filter(
tree_id=self.tree_id,
lft__lt=self.lft,
rgt__gt=self.rgt)
def is_descendant_of(self, node):
"""
:returns: ``True`` if the node if a descendant of another node given
as an argument, else, returns ``False``
See: :meth:`treebeard.Node.is_descendant_of`
"""
return self.tree_id == node.tree_id and \
self.lft > node.lft and \
self.rgt < node.rgt
def get_parent(self, update=False):
"""
:returns: the parent node of the current node object.
Caches the result in the object itself to help in loops.
See: :meth:`treebeard.Node.get_parent`
"""
if self.is_root():
return
try:
if update:
del self._cached_parent_obj
else:
return self._cached_parent_obj
except AttributeError:
pass
# parent = our most direct ancestor
self._cached_parent_obj = self.get_ancestors().reverse()[0]
return self._cached_parent_obj
@classmethod
def get_root_nodes(cls):
"""
:returns: A queryset containing the root nodes in the tree.
Example::
MyNodeModel.get_root_nodes()
"""
return cls.objects.filter(lft=1)
class Meta:
"""
Abstract model.
"""
abstract = True