bg update to clear out duplicate outbound_device_list_pokes (#7193)

We seem to have some duplicates, which could do with being cleared out.

tests/storage/test_database.py

@@ -0,0 +1,52 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.storage.database import make_tuple_comparison_clause
+from synapse.storage.engines import BaseDatabaseEngine
+
+from tests import unittest
+
+
+def _stub_db_engine(**kwargs) -> BaseDatabaseEngine:
+    # returns a DatabaseEngine, circumventing the abc mechanism
+    # any kwargs are set as attributes on the class before instantiating it
+    t = type(
+        "TestBaseDatabaseEngine",
+        (BaseDatabaseEngine,),
+        dict(BaseDatabaseEngine.__dict__),
+    )
+    # defeat the abc mechanism
+    t.__abstractmethods__ = set()
+    for k, v in kwargs.items():
+        setattr(t, k, v)
+    return t(None, None)
+
+
+class TupleComparisonClauseTestCase(unittest.TestCase):
+    def test_native_tuple_comparison(self):
+        db_engine = _stub_db_engine(supports_tuple_comparison=True)
+        clause, args = make_tuple_comparison_clause(db_engine, [("a", 1), ("b", 2)])
+        self.assertEqual(clause, "(a,b) > (?,?)")
+        self.assertEqual(args, [1, 2])
+
+    def test_emulated_tuple_comparison(self):
+        db_engine = _stub_db_engine(supports_tuple_comparison=False)
+        clause, args = make_tuple_comparison_clause(
+            db_engine, [("a", 1), ("b", 2), ("c", 3)]
+        )
+        self.assertEqual(
+            clause, "(a >= ? AND (a > ? OR (b >= ? AND (b > ? OR c > ?))))"
+        )
+        self.assertEqual(args, [1, 1, 2, 2, 3])