category: remove left/right

category.py

@@ -16,30 +16,26 @@ class Category(tree(separator=' / '), ModelSQL, ModelView):
     name = fields.Char(string='Name', required=True, translate=True)
 
     parent = fields.Many2One(string='Parent', select=True,
-        model_name='cashbook.bookcategory', ondelete='CASCADE',
-        left='left', right='right')
+        model_name='cashbook.bookcategory', ondelete='CASCADE')
     childs = fields.One2Many(string='Children', field='parent',
         model_name='cashbook.bookcategory')
-    left = fields.Integer(string='Left', required=True, select=True)
-    right = fields.Integer(string='Right', required=True, select=True)
 
     cashbooks = fields.Many2Many(string='Cashbooks',
         relation_name='cashbook.bookcategory-rel',
         origin='category', target='cashbook')
 
+    @classmethod
+    def __register__(cls, module_name):
+        super(Category, cls).__register__(module_name)
+        table = cls.__table_handler__(module_name)
+        table.drop_column('left')
+        table.drop_column('right')
+
     @classmethod
     def __setup__(cls):
         super(Category, cls).__setup__()
         cls._order.insert(0, ('rec_name', 'ASC'))
 
-    @staticmethod
-    def default_left():
-        return 0
-
-    @staticmethod
-    def default_right():
-        return 0
-
     @staticmethod
     def default_company():
         return Transaction().context.get('company') or None