Migrates tree_id from an Integer to Unicode(32)

sqlalchemy_mptt/events.py

@@ -15,6 +15,7 @@
 from sqlalchemy.orm import object_session
 from sqlalchemy.orm.base import NO_VALUE
 from sqlalchemy.sql import func
+import uuid
 
 
 def _insert_subtree(table, connection, node_size,
@@ -73,8 +74,7 @@ def mptt_before_insert(mapper, connection, instance):
         instance.left = 1
         instance.right = 2
         instance.level = 1
-        tree_id = connection.scalar(
-            select([func.max(table.c.tree_id) + 1])) or 1
+        tree_id = str(uuid.uuid4())
         instance.tree_id = tree_id
     else:
         (parent_pos_left,
@@ -197,7 +197,7 @@ def mptt_before_update(mapper, connection, instance):
                             'is_parent': False}
         # if move_before to top level
         elif not right_sibling_parent:
-            left_sibling_tree_id = right_sibling_tree_id - 1
+            left_sibling_tree_id = str(uuid.uuid4())
 
     # if placed after a particular node
     if hasattr(instance, 'mptt_move_after'):
@@ -296,18 +296,7 @@ def mptt_before_update(mapper, connection, instance):
                         parent_tree_id, parent_level, node_level, left_sibling,
                         table_pk)
     else:
-        # if insert after
-        if left_sibling_tree_id or left_sibling_tree_id == 0:
-            tree_id = left_sibling_tree_id + 1
-            connection.execute(
-                table.update(table.c.tree_id > left_sibling_tree_id)
-                .values(tree_id=table.c.tree_id + 1)
-            )
-        # if just insert
-        else:
-            tree_id = connection.scalar(
-                select([func.max(table.c.tree_id) + 1]))
-
+        tree_id = str(uuid.uuid4())
         connection.execute(
             table.update(table_pk.in_(subtree))
             .values(

sqlalchemy_mptt/mixins.py

@@ -10,7 +10,7 @@
 """
 SQLAlchemy nested sets mixin
 """
-from sqlalchemy import Index, Column, Integer, ForeignKey, desc, asc
+from sqlalchemy import Index, Column, Integer, ForeignKey, desc, asc, Unicode
 from sqlalchemy.orm import backref, relationship, object_session
 from sqlalchemy.orm.session import Session
 from sqlalchemy.ext.declarative import declared_attr
@@ -67,7 +67,7 @@ def get_pk_column(cls):
 
     @declared_attr
     def tree_id(cls):
-        return Column("tree_id", Integer)
+        return Column("tree_id", Unicode(32))
 
     @declared_attr
     def parent_id(cls):

sqlalchemy_mptt/tests/__init__.py

@@ -112,14 +112,16 @@ def test_session_expire_for_move_after_to_new_tree(self):
         node.move_after('1')
         self.session.flush()
 
-        self.assertEqual(node.tree_id, 2)
+        node = self.session.query(self.model). \
+            filter(self.model.get_pk_column() == 4).one()
+
         self.assertEqual(node.level, 1)
         self.assertEqual(node.parent_id, None)
 
-        self.assertEqual(children[0].tree_id, 2)
+        self.assertEqual(children[0].tree_id, node.tree_id)
         self.assertEqual(children[0].parent_id, 4)
         self.assertEqual(children[0].level, 2)
 
-        self.assertEqual(children[1].tree_id, 2)
+        self.assertEqual(children[1].tree_id, node.tree_id)
         self.assertEqual(children[1].parent_id, 4)
         self.assertEqual(children[1].level, 2)