Mercurial > agora-palash
view apps/mptt/managers.py @ 42:ab608f27ecd5
Copy preliminary django-paste code for snippets along with mptt. Works clunkily. Still need to adapt it for Agora.
author | Jordi Gutiérrez Hermoso <jordigh@gmail.com> |
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date | Thu, 29 Jul 2010 00:25:30 -0500 |
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""" A custom manager for working with trees of objects. """ from django.db import connection, models, transaction from django.utils.translation import ugettext as _ from agora.apps.mptt.exceptions import InvalidMove __all__ = ('TreeManager',) qn = connection.ops.quote_name COUNT_SUBQUERY = """( SELECT COUNT(*) FROM %(rel_table)s WHERE %(mptt_fk)s = %(mptt_table)s.%(mptt_pk)s )""" CUMULATIVE_COUNT_SUBQUERY = """( SELECT COUNT(*) FROM %(rel_table)s WHERE %(mptt_fk)s IN ( SELECT m2.%(mptt_pk)s FROM %(mptt_table)s m2 WHERE m2.%(tree_id)s = %(mptt_table)s.%(tree_id)s AND m2.%(left)s BETWEEN %(mptt_table)s.%(left)s AND %(mptt_table)s.%(right)s ) )""" class TreeManager(models.Manager): """ A manager for working with trees of objects. """ def __init__(self, parent_attr, left_attr, right_attr, tree_id_attr, level_attr): """ Tree attributes for the model being managed are held as attributes of this manager for later use, since it will be using them a **lot**. """ super(TreeManager, self).__init__() self.parent_attr = parent_attr self.left_attr = left_attr self.right_attr = right_attr self.tree_id_attr = tree_id_attr self.level_attr = level_attr def add_related_count(self, queryset, rel_model, rel_field, count_attr, cumulative=False): """ Adds a related item count to a given ``QuerySet`` using its ``extra`` method, for a ``Model`` class which has a relation to this ``Manager``'s ``Model`` class. Arguments: ``rel_model`` A ``Model`` class which has a relation to this `Manager``'s ``Model`` class. ``rel_field`` The name of the field in ``rel_model`` which holds the relation. ``count_attr`` The name of an attribute which should be added to each item in this ``QuerySet``, containing a count of how many instances of ``rel_model`` are related to it through ``rel_field``. ``cumulative`` If ``True``, the count will be for each item and all of its descendants, otherwise it will be for each item itself. """ opts = self.model._meta if cumulative: subquery = CUMULATIVE_COUNT_SUBQUERY % { 'rel_table': qn(rel_model._meta.db_table), 'mptt_fk': qn(rel_model._meta.get_field(rel_field).column), 'mptt_table': qn(opts.db_table), 'mptt_pk': qn(opts.pk.column), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), 'left': qn(opts.get_field(self.left_attr).column), 'right': qn(opts.get_field(self.right_attr).column), } else: subquery = COUNT_SUBQUERY % { 'rel_table': qn(rel_model._meta.db_table), 'mptt_fk': qn(rel_model._meta.get_field(rel_field).column), 'mptt_table': qn(opts.db_table), 'mptt_pk': qn(opts.pk.column), } return queryset.extra(select={count_attr: subquery}) def get_query_set(self): """ Returns a ``QuerySet`` which contains all tree items, ordered in such a way that that root nodes appear in tree id order and their subtrees appear in depth-first order. """ return super(TreeManager, self).get_query_set().order_by( self.tree_id_attr, self.left_attr) def insert_node(self, node, target, position='last-child', commit=False): """ Sets up the tree state for ``node`` (which has not yet been inserted into in the database) so it will be positioned relative to a given ``target`` node as specified by ``position`` (when appropriate) it is inserted, with any neccessary space already having been made for it. A ``target`` of ``None`` indicates that ``node`` should be the last root node. If ``commit`` is ``True``, ``node``'s ``save()`` method will be called before it is returned. """ if node.pk: raise ValueError(_('Cannot insert a node which has already been saved.')) if target is None: setattr(node, self.left_attr, 1) setattr(node, self.right_attr, 2) setattr(node, self.level_attr, 0) setattr(node, self.tree_id_attr, self._get_next_tree_id()) setattr(node, self.parent_attr, None) elif target.is_root_node() and position in ['left', 'right']: target_tree_id = getattr(target, self.tree_id_attr) if position == 'left': tree_id = target_tree_id space_target = target_tree_id - 1 else: tree_id = target_tree_id + 1 space_target = target_tree_id self._create_tree_space(space_target) setattr(node, self.left_attr, 1) setattr(node, self.right_attr, 2) setattr(node, self.level_attr, 0) setattr(node, self.tree_id_attr, tree_id) setattr(node, self.parent_attr, None) else: setattr(node, self.left_attr, 0) setattr(node, self.level_attr, 0) space_target, level, left, parent = \ self._calculate_inter_tree_move_values(node, target, position) tree_id = getattr(parent, self.tree_id_attr) self._create_space(2, space_target, tree_id) setattr(node, self.left_attr, -left) setattr(node, self.right_attr, -left + 1) setattr(node, self.level_attr, -level) setattr(node, self.tree_id_attr, tree_id) setattr(node, self.parent_attr, parent) if commit: node.save() return node def move_node(self, node, target, position='last-child'): """ Moves ``node`` relative to a given ``target`` node as specified by ``position`` (when appropriate), by examining both nodes and calling the appropriate method to perform the move. A ``target`` of ``None`` indicates that ``node`` should be turned into a root node. Valid values for ``position`` are ``'first-child'``, ``'last-child'``, ``'left'`` or ``'right'``. ``node`` will be modified to reflect its new tree state in the database. This method explicitly checks for ``node`` being made a sibling of a root node, as this is a special case due to our use of tree ids to order root nodes. """ if target is None: if node.is_child_node(): self._make_child_root_node(node) elif target.is_root_node() and position in ['left', 'right']: self._make_sibling_of_root_node(node, target, position) else: if node.is_root_node(): self._move_root_node(node, target, position) else: self._move_child_node(node, target, position) transaction.commit_unless_managed() def root_node(self, tree_id): """ Returns the root node of the tree with the given id. """ return self.get(**{ self.tree_id_attr: tree_id, '%s__isnull' % self.parent_attr: True, }) def root_nodes(self): """ Creates a ``QuerySet`` containing root nodes. """ return self.filter(**{'%s__isnull' % self.parent_attr: True}) def _calculate_inter_tree_move_values(self, node, target, position): """ Calculates values required when moving ``node`` relative to ``target`` as specified by ``position``. """ left = getattr(node, self.left_attr) level = getattr(node, self.level_attr) target_left = getattr(target, self.left_attr) target_right = getattr(target, self.right_attr) target_level = getattr(target, self.level_attr) if position == 'last-child' or position == 'first-child': if position == 'last-child': space_target = target_right - 1 else: space_target = target_left level_change = level - target_level - 1 parent = target elif position == 'left' or position == 'right': if position == 'left': space_target = target_left - 1 else: space_target = target_right level_change = level - target_level parent = getattr(target, self.parent_attr) else: raise ValueError(_('An invalid position was given: %s.') % position) left_right_change = left - space_target - 1 return space_target, level_change, left_right_change, parent def _close_gap(self, size, target, tree_id): """ Closes a gap of a certain ``size`` after the given ``target`` point in the tree identified by ``tree_id``. """ self._manage_space(-size, target, tree_id) def _create_space(self, size, target, tree_id): """ Creates a space of a certain ``size`` after the given ``target`` point in the tree identified by ``tree_id``. """ self._manage_space(size, target, tree_id) def _create_tree_space(self, target_tree_id): """ Creates space for a new tree by incrementing all tree ids greater than ``target_tree_id``. """ opts = self.model._meta cursor = connection.cursor() cursor.execute(""" UPDATE %(table)s SET %(tree_id)s = %(tree_id)s + 1 WHERE %(tree_id)s > %%s""" % { 'table': qn(opts.db_table), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), }, [target_tree_id]) def _get_next_tree_id(self): """ Determines the next largest unused tree id for the tree managed by this manager. """ opts = self.model._meta cursor = connection.cursor() cursor.execute('SELECT MAX(%s) FROM %s' % ( qn(opts.get_field(self.tree_id_attr).column), qn(opts.db_table))) row = cursor.fetchone() return row[0] and (row[0] + 1) or 1 def _inter_tree_move_and_close_gap(self, node, level_change, left_right_change, new_tree_id, parent_pk=None): """ Removes ``node`` from its current tree, with the given set of changes being applied to ``node`` and its descendants, closing the gap left by moving ``node`` as it does so. If ``parent_pk`` is ``None``, this indicates that ``node`` is being moved to a brand new tree as its root node, and will thus have its parent field set to ``NULL``. Otherwise, ``node`` will have ``parent_pk`` set for its parent field. """ opts = self.model._meta inter_tree_move_query = """ UPDATE %(table)s SET %(level)s = CASE WHEN %(left)s >= %%s AND %(left)s <= %%s THEN %(level)s - %%s ELSE %(level)s END, %(tree_id)s = CASE WHEN %(left)s >= %%s AND %(left)s <= %%s THEN %%s ELSE %(tree_id)s END, %(left)s = CASE WHEN %(left)s >= %%s AND %(left)s <= %%s THEN %(left)s - %%s WHEN %(left)s > %%s THEN %(left)s - %%s ELSE %(left)s END, %(right)s = CASE WHEN %(right)s >= %%s AND %(right)s <= %%s THEN %(right)s - %%s WHEN %(right)s > %%s THEN %(right)s - %%s ELSE %(right)s END, %(parent)s = CASE WHEN %(pk)s = %%s THEN %(new_parent)s ELSE %(parent)s END WHERE %(tree_id)s = %%s""" % { 'table': qn(opts.db_table), 'level': qn(opts.get_field(self.level_attr).column), 'left': qn(opts.get_field(self.left_attr).column), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), 'right': qn(opts.get_field(self.right_attr).column), 'parent': qn(opts.get_field(self.parent_attr).column), 'pk': qn(opts.pk.column), 'new_parent': parent_pk is None and 'NULL' or '%s', } left = getattr(node, self.left_attr) right = getattr(node, self.right_attr) gap_size = right - left + 1 gap_target_left = left - 1 params = [ left, right, level_change, left, right, new_tree_id, left, right, left_right_change, gap_target_left, gap_size, left, right, left_right_change, gap_target_left, gap_size, node.pk, getattr(node, self.tree_id_attr) ] if parent_pk is not None: params.insert(-1, parent_pk) cursor = connection.cursor() cursor.execute(inter_tree_move_query, params) def _make_child_root_node(self, node, new_tree_id=None): """ Removes ``node`` from its tree, making it the root node of a new tree. If ``new_tree_id`` is not specified a new tree id will be generated. ``node`` will be modified to reflect its new tree state in the database. """ left = getattr(node, self.left_attr) right = getattr(node, self.right_attr) level = getattr(node, self.level_attr) tree_id = getattr(node, self.tree_id_attr) if not new_tree_id: new_tree_id = self._get_next_tree_id() left_right_change = left - 1 self._inter_tree_move_and_close_gap(node, level, left_right_change, new_tree_id) # Update the node to be consistent with the updated # tree in the database. setattr(node, self.left_attr, left - left_right_change) setattr(node, self.right_attr, right - left_right_change) setattr(node, self.level_attr, 0) setattr(node, self.tree_id_attr, new_tree_id) setattr(node, self.parent_attr, None) def _make_sibling_of_root_node(self, node, target, position): """ Moves ``node``, making it a sibling of the given ``target`` root node as specified by ``position``. ``node`` will be modified to reflect its new tree state in the database. Since we use tree ids to reduce the number of rows affected by tree mangement during insertion and deletion, root nodes are not true siblings; thus, making an item a sibling of a root node is a special case which involves shuffling tree ids around. """ if node == target: raise InvalidMove(_('A node may not be made a sibling of itself.')) opts = self.model._meta tree_id = getattr(node, self.tree_id_attr) target_tree_id = getattr(target, self.tree_id_attr) if node.is_child_node(): if position == 'left': space_target = target_tree_id - 1 new_tree_id = target_tree_id elif position == 'right': space_target = target_tree_id new_tree_id = target_tree_id + 1 else: raise ValueError(_('An invalid position was given: %s.') % position) self._create_tree_space(space_target) if tree_id > space_target: # The node's tree id has been incremented in the # database - this change must be reflected in the node # object for the method call below to operate on the # correct tree. setattr(node, self.tree_id_attr, tree_id + 1) self._make_child_root_node(node, new_tree_id) else: if position == 'left': if target_tree_id > tree_id: left_sibling = target.get_previous_sibling() if node == left_sibling: return new_tree_id = getattr(left_sibling, self.tree_id_attr) lower_bound, upper_bound = tree_id, new_tree_id shift = -1 else: new_tree_id = target_tree_id lower_bound, upper_bound = new_tree_id, tree_id shift = 1 elif position == 'right': if target_tree_id > tree_id: new_tree_id = target_tree_id lower_bound, upper_bound = tree_id, target_tree_id shift = -1 else: right_sibling = target.get_next_sibling() if node == right_sibling: return new_tree_id = getattr(right_sibling, self.tree_id_attr) lower_bound, upper_bound = new_tree_id, tree_id shift = 1 else: raise ValueError(_('An invalid position was given: %s.') % position) root_sibling_query = """ UPDATE %(table)s SET %(tree_id)s = CASE WHEN %(tree_id)s = %%s THEN %%s ELSE %(tree_id)s + %%s END WHERE %(tree_id)s >= %%s AND %(tree_id)s <= %%s""" % { 'table': qn(opts.db_table), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), } cursor = connection.cursor() cursor.execute(root_sibling_query, [tree_id, new_tree_id, shift, lower_bound, upper_bound]) setattr(node, self.tree_id_attr, new_tree_id) def _manage_space(self, size, target, tree_id): """ Manages spaces in the tree identified by ``tree_id`` by changing the values of the left and right columns by ``size`` after the given ``target`` point. """ opts = self.model._meta space_query = """ UPDATE %(table)s SET %(left)s = CASE WHEN %(left)s > %%s THEN %(left)s + %%s ELSE %(left)s END, %(right)s = CASE WHEN %(right)s > %%s THEN %(right)s + %%s ELSE %(right)s END WHERE %(tree_id)s = %%s AND (%(left)s > %%s OR %(right)s > %%s)""" % { 'table': qn(opts.db_table), 'left': qn(opts.get_field(self.left_attr).column), 'right': qn(opts.get_field(self.right_attr).column), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), } cursor = connection.cursor() cursor.execute(space_query, [target, size, target, size, tree_id, target, target]) def _move_child_node(self, node, target, position): """ Calls the appropriate method to move child node ``node`` relative to the given ``target`` node as specified by ``position``. """ tree_id = getattr(node, self.tree_id_attr) target_tree_id = getattr(target, self.tree_id_attr) if (getattr(node, self.tree_id_attr) == getattr(target, self.tree_id_attr)): self._move_child_within_tree(node, target, position) else: self._move_child_to_new_tree(node, target, position) def _move_child_to_new_tree(self, node, target, position): """ Moves child node ``node`` to a different tree, inserting it relative to the given ``target`` node in the new tree as specified by ``position``. ``node`` will be modified to reflect its new tree state in the database. """ left = getattr(node, self.left_attr) right = getattr(node, self.right_attr) level = getattr(node, self.level_attr) target_left = getattr(target, self.left_attr) target_right = getattr(target, self.right_attr) target_level = getattr(target, self.level_attr) tree_id = getattr(node, self.tree_id_attr) new_tree_id = getattr(target, self.tree_id_attr) space_target, level_change, left_right_change, parent = \ self._calculate_inter_tree_move_values(node, target, position) tree_width = right - left + 1 # Make space for the subtree which will be moved self._create_space(tree_width, space_target, new_tree_id) # Move the subtree self._inter_tree_move_and_close_gap(node, level_change, left_right_change, new_tree_id, parent.pk) # Update the node to be consistent with the updated # tree in the database. setattr(node, self.left_attr, left - left_right_change) setattr(node, self.right_attr, right - left_right_change) setattr(node, self.level_attr, level - level_change) setattr(node, self.tree_id_attr, new_tree_id) setattr(node, self.parent_attr, parent) def _move_child_within_tree(self, node, target, position): """ Moves child node ``node`` within its current tree relative to the given ``target`` node as specified by ``position``. ``node`` will be modified to reflect its new tree state in the database. """ left = getattr(node, self.left_attr) right = getattr(node, self.right_attr) level = getattr(node, self.level_attr) width = right - left + 1 tree_id = getattr(node, self.tree_id_attr) target_left = getattr(target, self.left_attr) target_right = getattr(target, self.right_attr) target_level = getattr(target, self.level_attr) if position == 'last-child' or position == 'first-child': if node == target: raise InvalidMove(_('A node may not be made a child of itself.')) elif left < target_left < right: raise InvalidMove(_('A node may not be made a child of any of its descendants.')) if position == 'last-child': if target_right > right: new_left = target_right - width new_right = target_right - 1 else: new_left = target_right new_right = target_right + width - 1 else: if target_left > left: new_left = target_left - width + 1 new_right = target_left else: new_left = target_left + 1 new_right = target_left + width level_change = level - target_level - 1 parent = target elif position == 'left' or position == 'right': if node == target: raise InvalidMove(_('A node may not be made a sibling of itself.')) elif left < target_left < right: raise InvalidMove(_('A node may not be made a sibling of any of its descendants.')) if position == 'left': if target_left > left: new_left = target_left - width new_right = target_left - 1 else: new_left = target_left new_right = target_left + width - 1 else: if target_right > right: new_left = target_right - width + 1 new_right = target_right else: new_left = target_right + 1 new_right = target_right + width level_change = level - target_level parent = getattr(target, self.parent_attr) else: raise ValueError(_('An invalid position was given: %s.') % position) left_boundary = min(left, new_left) right_boundary = max(right, new_right) left_right_change = new_left - left gap_size = width if left_right_change > 0: gap_size = -gap_size opts = self.model._meta # The level update must come before the left update to keep # MySQL happy - left seems to refer to the updated value # immediately after its update has been specified in the query # with MySQL, but not with SQLite or Postgres. move_subtree_query = """ UPDATE %(table)s SET %(level)s = CASE WHEN %(left)s >= %%s AND %(left)s <= %%s THEN %(level)s - %%s ELSE %(level)s END, %(left)s = CASE WHEN %(left)s >= %%s AND %(left)s <= %%s THEN %(left)s + %%s WHEN %(left)s >= %%s AND %(left)s <= %%s THEN %(left)s + %%s ELSE %(left)s END, %(right)s = CASE WHEN %(right)s >= %%s AND %(right)s <= %%s THEN %(right)s + %%s WHEN %(right)s >= %%s AND %(right)s <= %%s THEN %(right)s + %%s ELSE %(right)s END, %(parent)s = CASE WHEN %(pk)s = %%s THEN %%s ELSE %(parent)s END WHERE %(tree_id)s = %%s""" % { 'table': qn(opts.db_table), 'level': qn(opts.get_field(self.level_attr).column), 'left': qn(opts.get_field(self.left_attr).column), 'right': qn(opts.get_field(self.right_attr).column), 'parent': qn(opts.get_field(self.parent_attr).column), 'pk': qn(opts.pk.column), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), } cursor = connection.cursor() cursor.execute(move_subtree_query, [ left, right, level_change, left, right, left_right_change, left_boundary, right_boundary, gap_size, left, right, left_right_change, left_boundary, right_boundary, gap_size, node.pk, parent.pk, tree_id]) # Update the node to be consistent with the updated # tree in the database. setattr(node, self.left_attr, new_left) setattr(node, self.right_attr, new_right) setattr(node, self.level_attr, level - level_change) setattr(node, self.parent_attr, parent) def _move_root_node(self, node, target, position): """ Moves root node``node`` to a different tree, inserting it relative to the given ``target`` node as specified by ``position``. ``node`` will be modified to reflect its new tree state in the database. """ left = getattr(node, self.left_attr) right = getattr(node, self.right_attr) level = getattr(node, self.level_attr) tree_id = getattr(node, self.tree_id_attr) new_tree_id = getattr(target, self.tree_id_attr) width = right - left + 1 if node == target: raise InvalidMove(_('A node may not be made a child of itself.')) elif tree_id == new_tree_id: raise InvalidMove(_('A node may not be made a child of any of its descendants.')) space_target, level_change, left_right_change, parent = \ self._calculate_inter_tree_move_values(node, target, position) # Create space for the tree which will be inserted self._create_space(width, space_target, new_tree_id) # Move the root node, making it a child node opts = self.model._meta move_tree_query = """ UPDATE %(table)s SET %(level)s = %(level)s - %%s, %(left)s = %(left)s - %%s, %(right)s = %(right)s - %%s, %(tree_id)s = %%s, %(parent)s = CASE WHEN %(pk)s = %%s THEN %%s ELSE %(parent)s END WHERE %(left)s >= %%s AND %(left)s <= %%s AND %(tree_id)s = %%s""" % { 'table': qn(opts.db_table), 'level': qn(opts.get_field(self.level_attr).column), 'left': qn(opts.get_field(self.left_attr).column), 'right': qn(opts.get_field(self.right_attr).column), 'tree_id': qn(opts.get_field(self.tree_id_attr).column), 'parent': qn(opts.get_field(self.parent_attr).column), 'pk': qn(opts.pk.column), } cursor = connection.cursor() cursor.execute(move_tree_query, [level_change, left_right_change, left_right_change, new_tree_id, node.pk, parent.pk, left, right, tree_id]) # Update the former root node to be consistent with the updated # tree in the database. setattr(node, self.left_attr, left - left_right_change) setattr(node, self.right_attr, right - left_right_change) setattr(node, self.level_attr, level - level_change) setattr(node, self.tree_id_attr, new_tree_id) setattr(node, self.parent_attr, parent)