Return some room data in Sliding Sync `/sync` (#17320)

 - Timeline events
 - Stripped `invite_state`

Based on [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): Sliding Sync

1 files changed, 4 insertions, 1 deletions

diff --git a/synapse/storage/schema/main/delta/42/current_state_delta.sql b/synapse/storage/schema/main/delta/42/current_state_delta.sql

index 876b61e6a5..3d2fd69480 100644
--- a/synapse/storage/schema/main/delta/42/current_state_delta.sql
+++ b/synapse/storage/schema/main/delta/42/current_state_delta.sql
@@ -32,7 +32,10 @@
  * limitations under the License.
  */
 
-
+-- Tracks what the server thinks is the current state of the room as time goes. It does
+-- not track how state progresses from the beginning of the room. So for example, when
+-- you remotely join a room, the first rows will just be the state when you joined and
+-- progress from there.
 CREATE TABLE current_state_delta_stream (
     stream_id BIGINT NOT NULL,
     room_id TEXT NOT NULL,