- Fixed an issue in baked queries where the .get() method, used either

directly or within lazy loads, didn't consider the mapper's "get clause"
as part of the cache key, causing bound parameter mismatches if the
clause got re-generated.  This clause is cached by mappers
on the fly but in highly concurrent scenarios may be generated more
than once when first accessed.
fixes #3597

(cherry picked from commit b0308a7b3a)

doc/build/changelog/changelog_10.rst

@@ -18,6 +18,18 @@
 .. changelog::
     :version: 1.0.10
 
+    .. change::
+        :tags: bug, ext
+        :versions: 1.1.0b1
+        :tickets: 3597
+
+        Fixed an issue in baked queries where the .get() method, used either
+        directly or within lazy loads, didn't consider the mapper's "get clause"
+        as part of the cache key, causing bound parameter mismatches if the
+        clause got re-generated.  This clause is cached by mappers
+        on the fly but in highly concurrent scenarios may be generated more
+        than once when first accessed.
+
     .. change::
         :tags: feature, sql
         :versions: 1.1.0b1

lib/sqlalchemy/ext/baked.py

@@ -355,6 +355,12 @@ class Result(object):
         # (remember, we can map to an OUTER JOIN)
         bq = self.bq
 
+        # add the clause we got from mapper._get_clause to the cache
+        # key so that if a race causes multiple calls to _get_clause,
+        # we've cached on ours
+        bq = bq._clone()
+        bq._cache_key += (_get_clause, )
+
         bq = bq.with_criteria(setup, tuple(elem is None for elem in ident))
 
         params = dict([

test/ext/test_baked.py

@@ -270,6 +270,30 @@ class LikeQueryTest(BakedTest):
             eq_(u2.name, 'chuck')
         self.assert_sql_count(testing.db, go, 0)
 
+    def test_get_includes_getclause(self):
+        # test issue #3597
+        User = self.classes.User
+
+        bq = self.bakery(lambda s: s.query(User))
+
+        for i in range(5):
+            sess = Session()
+            u1 = bq(sess).get(7)
+            eq_(u1.name, 'jack')
+
+        eq_(len(bq._bakery), 2)
+
+        # simulate race where mapper._get_clause
+        # may be generated more than once
+        from sqlalchemy import inspect
+        del inspect(User).__dict__['_get_clause']
+
+        for i in range(5):
+            sess = Session()
+            u1 = bq(sess).get(7)
+            eq_(u1.name, 'jack')
+        eq_(len(bq._bakery), 4)
+
 
 class ResultTest(BakedTest):
     __backend__ = True