Improve perf of sync device lists (#17191)

It's almost always more efficient to query the rooms that have device
list changes, rather than looking at the list of all users whose devices
have changed and then look for shared rooms.

1 files changed, 2 insertions, 15 deletions

diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index 8dbcb3f5a0..d98f0593bc 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -70,10 +70,7 @@ from synapse.types import (
 from synapse.util import json_decoder, json_encoder
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.caches.lrucache import LruCache
-from synapse.util.caches.stream_change_cache import (
-    AllEntitiesChangedResult,
-    StreamChangeCache,
-)
+from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.cancellation import cancellable
 from synapse.util.iterutils import batch_iter
 from synapse.util.stringutils import shortstr
@@ -832,16 +829,6 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
         )
         return {device[0]: db_to_json(device[1]) for device in devices}
 
-    def get_cached_device_list_changes(
-        self,
-        from_key: int,
-    ) -> AllEntitiesChangedResult:
-        """Get set of users whose devices have changed since `from_key`, or None
-        if that information is not in our cache.
-        """
-
-        return self._device_list_stream_cache.get_all_entities_changed(from_key)
-
     @cancellable
     async def get_all_devices_changed(
         self,
@@ -1475,7 +1462,7 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
 
         sql = """
             SELECT DISTINCT user_id FROM device_lists_changes_in_room
-            WHERE {clause} AND stream_id >= ?
+            WHERE {clause} AND stream_id > ?
         """
 
         def _get_device_list_changes_in_rooms_txn(