From deb7e76a42fac9995174f30baa365b4d03ddee3c Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Sat, 25 Feb 2012 14:34:02 -0500
Subject: [PATCH] - [feature] Added "no_autoflush" context manager to Session,
 used with with: will temporarily disable autoflush.

---
 CHANGES                         |  4 ++++
 lib/sqlalchemy/orm/session.py   | 28 ++++++++++++++++++++++++++++
 lib/sqlalchemy/util/__init__.py |  2 +-
 lib/sqlalchemy/util/compat.py   |  6 ++++++
 test/orm/test_session.py        | 17 +++++++++++++++++
 5 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index d45f616a00..867ed01186 100644
--- a/CHANGES
+++ b/CHANGES
@@ -6,6 +6,10 @@ CHANGES
 0.7.6
 =====
 - orm
+  - [feature] Added "no_autoflush" context
+    manager to Session, used with with:
+    will temporarily disable autoflush.
+
   - [bug] Fixed bug whereby MappedCollection
     would not get the appropriate collection
     instrumentation if it were only used
diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index ba6ceaeeca..d01c1598ae 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -978,6 +978,34 @@ class Session(object):
 
         return self._query_cls(entities, self, **kwargs)
 
+    @property
+    @util.contextmanager
+    def no_autoflush(self):
+        """Return a context manager that disables autoflush.
+        
+        e.g.::
+        
+            with session.no_autoflush:
+                
+                some_object = SomeClass()
+                session.add(some_object)
+                # won't autoflush
+                some_object.related_thing = session.query(SomeRelated).first()
+        
+        Operations that proceed within the ``with:`` block
+        will not be subject to flushes occurring upon query
+        access.  This is useful when initializing a series
+        of objects which involve existing database queries,
+        where the uncompleted object should not yet be flushed.
+        
+        New in 0.7.6.
+
+        """
+        autoflush = self.autoflush
+        self.autoflush = False
+        yield self
+        self.autoflush = autoflush
+
     def _autoflush(self):
         if self.autoflush and not self._flushing:
             self.flush()
diff --git a/lib/sqlalchemy/util/__init__.py b/lib/sqlalchemy/util/__init__.py
index 5712940258..13914aa7dc 100644
--- a/lib/sqlalchemy/util/__init__.py
+++ b/lib/sqlalchemy/util/__init__.py
@@ -7,7 +7,7 @@
 from compat import callable, cmp, reduce, defaultdict, py25_dict, \
     threading, py3k_warning, jython, pypy, win32, set_types, buffer, pickle, \
     update_wrapper, partial, md5_hex, decode_slice, dottedgetter,\
-    parse_qsl, any
+    parse_qsl, any, contextmanager
 
 from _collections import NamedTuple, ImmutableContainer, immutabledict, \
     Properties, OrderedProperties, ImmutableProperties, OrderedDict, \
diff --git a/lib/sqlalchemy/util/compat.py b/lib/sqlalchemy/util/compat.py
index 07652f3c6c..99b92b1e34 100644
--- a/lib/sqlalchemy/util/compat.py
+++ b/lib/sqlalchemy/util/compat.py
@@ -56,6 +56,12 @@ def buffer(x):
 buffer = buffer
 # end Py2K
 
+try:
+    from contextlib import contextmanager
+except ImportError:
+    def contextmanager(fn):
+        return fn
+
 try:
     from functools import update_wrapper
 except ImportError:
diff --git a/test/orm/test_session.py b/test/orm/test_session.py
index ac22455bdf..79852c7a4a 100644
--- a/test/orm/test_session.py
+++ b/test/orm/test_session.py
@@ -222,6 +222,23 @@ class SessionTest(_fixtures.FixtureTest):
         eq_(bind.connect().execute("select count(1) from users").scalar(), 1)
         sess.close()
 
+    @testing.requires.python26
+    def test_with_no_autoflush(self):
+        User, users = self.classes.User, self.tables.users
+
+        mapper(User, users)
+        sess = Session()
+
+        u = User()
+        u.name = 'ed'
+        sess.add(u)
+        def go(obj):
+            assert u not in sess.query(User).all()
+        testing.run_as_contextmanager(sess.no_autoflush, go)
+        assert u in sess.new
+        assert u in sess.query(User).all()
+        assert u not in sess.new
+
     def test_make_transient(self):
         users, User = self.tables.users, self.classes.User
 
-- 
2.47.2