defaults and constraints have optional parent

diff --git a/lib/sqlalchemy/schema.py b/lib/sqlalchemy/schema.py
index 6fc10c6cb1bd5214dfdf49511d89f9fe4c2227ca..5c7ec72b6cb6a29ee7f3ccbcd78e47b1673f3799 100644 (file)
--- a/lib/sqlalchemy/schema.py
+++ b/lib/sqlalchemy/schema.py
@@ -600,7 +600,7 @@ class DefaultGenerator(SchemaItem):
         except AttributeError:
             return self._metadata
     def _get_parent(self):
-        return self.column
+        return getattr(self, 'column', None)
     def _set_parent(self, column):
         self.column = column
         self._metadata = self.column.table.metadata
@@ -687,7 +687,7 @@ class Constraint(SchemaItem):
     def copy(self):
         raise NotImplementedError()
     def _get_parent(self):
-        return self.table
+        return getattr(self, 'table', None)
         
 class ForeignKeyConstraint(Constraint):
     """table-level foreign key constraint, represents a colleciton of ForeignKey objects."""