Stop using 'device_max_stream_id' (#7882)

It serves no purpose and updating everytime we write to the device inbox
stream means all such transactions will conflict, causing lots of
transaction failures and retries.

changelog.d/7882.misc

@@ -0,0 +1 @@
+Stop using `device_max_stream_id` table and just use `device_inbox.stream_id`.

synapse/replication/slave/storage/deviceinbox.py

@@ -26,7 +26,7 @@ class SlavedDeviceInboxStore(DeviceInboxWorkerStore, BaseSlavedStore):
     def __init__(self, database: Database, db_conn, hs):
         super(SlavedDeviceInboxStore, self).__init__(database, db_conn, hs)
         self._device_inbox_id_gen = SlavedIdTracker(
-            db_conn, "device_max_stream_id", "stream_id"
+            db_conn, "device_inbox", "stream_id"
         )
         self._device_inbox_stream_cache = StreamChangeCache(
             "DeviceInboxStreamChangeCache",

synapse/storage/data_stores/main/__init__.py

@@ -128,7 +128,7 @@ class DataStore(
             db_conn, "presence_stream", "stream_id"
         )
         self._device_inbox_id_gen = StreamIdGenerator(
-            db_conn, "device_max_stream_id", "stream_id"
+            db_conn, "device_inbox", "stream_id"
         )
         self._public_room_id_gen = StreamIdGenerator(
             db_conn, "public_room_list_stream", "stream_id"

synapse/storage/data_stores/main/deviceinbox.py

@@ -424,9 +424,6 @@ class DeviceInboxStore(DeviceInboxWorkerStore, DeviceInboxBackgroundUpdateStore)
     def _add_messages_to_local_device_inbox_txn(
         self, txn, stream_id, messages_by_user_then_device
     ):
-        sql = "UPDATE device_max_stream_id" " SET stream_id = ?" " WHERE stream_id < ?"
-        txn.execute(sql, (stream_id, stream_id))
-
         local_by_user_then_device = {}
         for user_id, messages_by_device in messages_by_user_then_device.items():
             messages_json_for_user = {}