From 9f72910c7c1cc70486c825ddc53d0b293f1b0d8b Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Tue, 8 Jan 2013 10:57:15 -0500
Subject: [PATCH] :meth:`.Query.merge_result` can now load rows from an outer
 join where an entity may be ``None`` without throwing an error.

[ticket:2640]
---
 doc/build/changelog/changelog_07.rst |  7 +++++++
 lib/sqlalchemy/orm/query.py          |  9 +++++----
 test/orm/test_loading.py             | 23 ++++++++++++++++++++++-
 3 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/doc/build/changelog/changelog_07.rst b/doc/build/changelog/changelog_07.rst
index b62e86df6b..fdf5c1fa28 100644
--- a/doc/build/changelog/changelog_07.rst
+++ b/doc/build/changelog/changelog_07.rst
@@ -27,6 +27,13 @@
       to the MSSQL dialect's "schema rendering"
       logic's failure to take .key into account.
 
+    .. change::
+        :tags: orm, bug
+        :tickets: 2640
+
+      :meth:`.Query.merge_result` can now load rows from an outer join
+      where an entity may be ``None`` without throwing an error.
+
     .. change::
         :tags: sqlite, bug
         :tickets: 2568
diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 1be9777f44..286dbf6b3e 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -2419,10 +2419,11 @@ class Query(object):
                 for row in iterator:
                     newrow = list(row)
                     for i in mapped_entities:
-                        newrow[i] = session._merge(
-                                attributes.instance_state(newrow[i]),
-                                attributes.instance_dict(newrow[i]),
-                                load=load, _recursive={})
+                        if newrow[i] is not None:
+                            newrow[i] = session._merge(
+                                    attributes.instance_state(newrow[i]),
+                                    attributes.instance_dict(newrow[i]),
+                                    load=load, _recursive={})
                     result.append(util.NamedTuple(newrow, keys))
 
             return iter(result)
diff --git a/test/orm/test_loading.py b/test/orm/test_loading.py
index 77afa17a0c..7b401a7cc1 100644
--- a/test/orm/test_loading.py
+++ b/test/orm/test_loading.py
@@ -1,5 +1,5 @@
 from test.orm import _fixtures
-from sqlalchemy.orm import Session, mapper
+from sqlalchemy.orm import Session, mapper, aliased
 from test.lib.testing import eq_
 from sqlalchemy.util import NamedTuple
 
@@ -89,3 +89,24 @@ class MergeResultTest(_fixtures.FixtureTest):
             [(1, 1), (2, 2), (7, 7), (8, 8)]
         )
         eq_(it[0].keys(), ['User', 'id'])
+
+    def test_none_entity(self):
+        s, (u1, u2, u3, u4) = self._fixture()
+        User = self.classes.User
+
+        ua = aliased(User)
+        q = s.query(User, ua)
+        kt = lambda *x: NamedTuple(x, ['User', 'useralias'])
+        collection = [kt(u1, u2), kt(u1, None), kt(u2, u3)]
+        it = q.merge_result(
+            collection
+        )
+        eq_(
+            [
+                (x and x.id or None, y and y.id or None)
+                for x, y in it
+            ],
+            [(u1.id, u2.id), (u1.id, None), (u2.id, u3.id)]
+        )
+
+
-- 
2.47.2