- The string keys that are used to determine the columns impacted

for an INSERT or UPDATE are now sorted when they contribute towards
the "compiled cache" cache key.   These keys were previously not
deterministically ordered, meaning the same statement could be
cached multiple times on equivalent keys, costing both in terms of
memory as well as performance.
fixes #3165

3 files changed, 58 insertions, 4 deletions

diff --git a/doc/build/changelog/changelog_09.rst b/doc/build/changelog/changelog_09.rst
index a797bfa29..0f92fb254 100644
--- a/doc/build/changelog/changelog_09.rst
+++ b/doc/build/changelog/changelog_09.rst
@@ -14,6 +14,18 @@
     :version: 0.9.8
 
     .. change::
+        :tags: bug, engine
+        :versions: 1.0.0
+        :tickets: 3165
+
+        The string keys that are used to determine the columns impacted
+        for an INSERT or UPDATE are now sorted when they contribute towards
+        the "compiled cache" cache key.   These keys were previously not
+        deterministically ordered, meaning the same statement could be
+        cached multiple times on equivalent keys, costing both in terms of
+        memory as well as performance.
+
+    .. change::
         :tags: bug, postgresql
         :versions: 1.0.0
         :tickets: 3159
diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 2dc4d43f2..65753b6dc 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -805,7 +805,7 @@ class Connection(Connectable):
 
         dialect = self.dialect
         if 'compiled_cache' in self._execution_options:
-            key = dialect, elem, tuple(keys), len(distilled_params) > 1
+            key = dialect, elem, tuple(sorted(keys)), len(distilled_params) > 1
             if key in self._execution_options['compiled_cache']:
                 compiled_sql = self._execution_options['compiled_cache'][key]
             else:
diff --git a/test/engine/test_execute.py b/test/engine/test_execute.py
index 291aee2f3..f65168552 100644
--- a/test/engine/test_execute.py
+++ b/test/engine/test_execute.py
@@ -688,6 +688,7 @@ class CompiledCacheTest(fixtures.TestBase):
                       Column('user_id', INT, primary_key=True,
                              test_needs_autoincrement=True),
                       Column('user_name', VARCHAR(20)),
+                      Column("extra_data", VARCHAR(20))
                       )
         metadata.create_all()
 
@@ -705,12 +706,53 @@ class CompiledCacheTest(fixtures.TestBase):
         cached_conn = conn.execution_options(compiled_cache=cache)
 
         ins = users.insert()
-        cached_conn.execute(ins, {'user_name': 'u1'})
-        cached_conn.execute(ins, {'user_name': 'u2'})
-        cached_conn.execute(ins, {'user_name': 'u3'})
+        with patch.object(
+            ins, "compile",
+                Mock(side_effect=ins.compile)) as compile_mock:
+            cached_conn.execute(ins, {'user_name': 'u1'})
+            cached_conn.execute(ins, {'user_name': 'u2'})
+            cached_conn.execute(ins, {'user_name': 'u3'})
+        eq_(compile_mock.call_count, 1)
         assert len(cache) == 1
         eq_(conn.execute("select count(*) from users").scalar(), 3)
 
+    def test_keys_independent_of_ordering(self):
+        conn = testing.db.connect()
+        conn.execute(
+            users.insert(),
+            {"user_id": 1, "user_name": "u1", "extra_data": "e1"})
+        cache = {}
+        cached_conn = conn.execution_options(compiled_cache=cache)
+
+        upd = users.update().where(users.c.user_id == bindparam("b_user_id"))
+
+        with patch.object(
+            upd, "compile",
+                Mock(side_effect=upd.compile)) as compile_mock:
+            cached_conn.execute(
+                upd, util.OrderedDict([
+                    ("b_user_id", 1),
+                    ("user_name", "u2"),
+                    ("extra_data", "e2")
+                ])
+            )
+            cached_conn.execute(
+                upd, util.OrderedDict([
+                    ("b_user_id", 1),
+                    ("extra_data", "e3"),
+                    ("user_name", "u3"),
+                ])
+            )
+            cached_conn.execute(
+                upd, util.OrderedDict([
+                    ("extra_data", "e4"),
+                    ("user_name", "u4"),
+                    ("b_user_id", 1),
+                ])
+            )
+        eq_(compile_mock.call_count, 1)
+        eq_(len(cache), 1)
+
 
 class MockStrategyTest(fixtures.TestBase):