- added close() method to Transaction. closes out a transaction using rollback

  if it's the outermost transaction, otherwise just ends without affecting
  the outer transaction.

- transactional and non-transactional Session integrates better with bound
  connection; a close() will ensure that connection transactional state is
  the same as that which existed on it before being bound to the Session.

2 files changed, 15 insertions, 1 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 8fe34bf3f..faeb00cc9 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -864,6 +864,20 @@ class Transaction(object):
     connection = property(lambda s:s._connection, doc="The Connection object referenced by this Transaction")
     is_active = property(lambda s:s._is_active)
 
+    def close(self):
+        """close this transaction.
+        
+        If this transaction is the base transaction in a begin/commit nesting, 
+        the transaction will rollback().  Otherwise, the method returns.
+        
+        This is used to cancel a Transaction without affecting the scope of
+        an enclosign transaction.
+        """
+        if not self._parent._is_active:
+            return
+        if self._parent is self:
+            self.rollback()
+        
     def rollback(self):
         if not self._parent._is_active:
             return
diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index f21d8d69b..5a91f8fbf 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -243,7 +243,7 @@ class SessionTransaction(object):
             if t[2]:
                 t[0].close()
             else:
-                t[1].rollback()
+                t[1].close()
         self.session.transaction = None
 
     def __enter__(self):