From 715d6cf3d10a71acd7726b7e00c3ff40b4559bc7 Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Sun, 30 Jun 2013 15:58:50 -0400
Subject: [PATCH] - additional fix for [ticket:2750] where on an update, we
 make sure the value is present

---
 lib/sqlalchemy/orm/mapper.py       |  3 ++-
 test/orm/inheritance/test_basic.py | 35 ++++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 12d2234d2d..9dfc1e267e 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -1053,7 +1053,8 @@ class Mapper(_InspectionAttr):
                         state.manager.mapper.polymorphic_identity, None)
 
             def _validate_polymorphic_identity(mapper, state, dict_):
-                if dict_[polymorphic_key] not in \
+                if polymorphic_key in dict_ and \
+                    dict_[polymorphic_key] not in \
                     mapper._acceptable_polymorphic_identities:
                     util.warn(
                                 "Flushing object %s with "
diff --git a/test/orm/inheritance/test_basic.py b/test/orm/inheritance/test_basic.py
index 99a008436f..41a167e724 100644
--- a/test/orm/inheritance/test_basic.py
+++ b/test/orm/inheritance/test_basic.py
@@ -555,11 +555,12 @@ class PolymorphicAttributeManagementTest(fixtures.MappedTest):
         Table('table_b', metadata,
            Column('id', Integer, ForeignKey('table_a.id'),
                                 primary_key=True),
-           Column('class_name', String(50))
+           Column('class_name', String(50)),
         )
         Table('table_c', metadata,
            Column('id', Integer, ForeignKey('table_b.id'),
-                                primary_key=True)
+                                primary_key=True),
+           Column('data', String(10))
         )
 
     @classmethod
@@ -684,6 +685,36 @@ class PolymorphicAttributeManagementTest(fixtures.MappedTest):
             sess.flush
         )
 
+    def test_not_set_on_upate(self):
+        C = self.classes.C
+
+        sess = Session()
+        c1 = C()
+        sess.add(c1)
+        sess.commit()
+        sess.expire(c1)
+
+        c1.data = 'foo'
+        sess.flush()
+
+    def test_validate_on_upate(self):
+        C = self.classes.C
+
+        sess = Session()
+        c1 = C()
+        sess.add(c1)
+        sess.commit()
+        sess.expire(c1)
+
+        c1.class_name = 'b'
+        assert_raises_message(
+            sa_exc.SAWarning,
+            "Flushing object %s with incompatible "
+            "polymorphic identity 'b'; the object may not "
+            "refresh and/or load correctly" % instance_str(c1),
+            sess.flush
+        )
+
 class CascadeTest(fixtures.MappedTest):
     """that cascades on polymorphic relationships continue
     cascading along the path of the instance's mapper, not
-- 
2.47.3