Don't return unknown entities in get_entities_changed

synapse/util/caches/stream_change_cache.py

@@ -74,19 +74,12 @@ def get_entities_changed(self, entities, stream_pos):
         assert type(stream_pos) is int
 
         if stream_pos >= self._earliest_known_stream_pos:
-            changed_entities = {
+            result = {
                 self._cache[k] for k in self._cache.islice(
                     start=self._cache.bisect_right(stream_pos),
                 )
             }
 
-            # we need to include entities which we don't know about, as well as
-            # those which are known to have changed since the stream pos.
-            result = {
-                e for e in entities
-                if e in changed_entities or e not in self._entity_to_key
-            }
-
             self.metrics.inc_hits()
         else:
             result = set(entities)

tests/util/test_stream_change_cache.py

@@ -141,8 +141,8 @@ def test_get_entities_changed(self):
         )
 
         # Query all the entries mid-way through the stream, but include one
-        # that doesn't exist in it. We should get back the one that doesn't
-        # exist, too.
+        # that doesn't exist in it. We shouldn't get back the one that doesn't
+        # exist.
         self.assertEqual(
             cache.get_entities_changed(
                 [
@@ -153,7 +153,7 @@ def test_get_entities_changed(self):
                 ],
                 stream_pos=2,
             ),
-            set(["[email protected]", "[email protected]", "[email protected]"]),
+            set(["[email protected]", "[email protected]"]),
         )
 
         # Query all the entries, but before the first known point. We will get