synapse/storage/databases/main/stream.py

@@ -123,8 +123,6 @@ class CurrentStateDeltaMembership:
         room_id: The room ID of the membership event.
         membership: The membership state of the user in the room
         sender: The person who sent the membership event
-        state_reset: Whether the membership in the room was changed without a
-            corresponding event (state reset).
     """
 
     event_id: Optional[str]
@@ -133,7 +131,6 @@ class CurrentStateDeltaMembership:
     room_id: str
     membership: str
     sender: Optional[str]
-    state_reset: bool
 
 
 def generate_pagination_where_clause(
@@ -849,15 +846,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             min_from_id = from_key.stream
             max_to_id = to_key.get_max_stream_pos()
 
-            args: List[Any] = [
+            args: List[Any] = [min_from_id, max_to_id, user_id, EventTypes.Member]
-                EventTypes.Member,
-                user_id,
-                user_id,
-                min_from_id,
-                max_to_id,
-                EventTypes.Member,
-                user_id,
-            ]
 
             # TODO: It would be good to assert that the `from_token`/`to_token` is >=
             # the first row in `current_state_delta_stream` for the rooms we're
@@ -870,44 +859,38 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             # `stream_ordering` is unique across the Synapse instance so this should
             # work fine.
             #
-            # We `COALESCE` the `stream_ordering` because we prefer the source of truth
+            # We `COALESCE` the `instance_name` and `stream_ordering` because we prefer
-            # from the `events` table. This gives slightly more accurate results when
+            # the source of truth from the events table. This gives slightly more
-            # available since `current_state_delta_stream` only tracks that the current
+            # accurate results when available since `current_state_delta_stream` only
-            # state is at this stream position (not what stream position the state event
+            # tracks that the current state is at this stream position (not what stream
-            # was added) and uses the *minimum* stream position for batches of events.
+            # position the state event was added) and batches events at the same
+            # `stream_id` in certain cases.
             #
-            # The extra `LEFT JOIN` by stream position are only needed to tell a state
+            # TODO: We need to add indexes for `current_state_delta_stream.event_id` and
-            # reset from the server leaving the room. Both cases have `event_id = null`
+            # `current_state_delta_stream.state_key`/`current_state_delta_stream.type`
-            # but if we can find a corresponding event at that stream position, then we
+            # for this to be efficient.
-            # know it was just the server leaving the room.
             sql = """
                 SELECT
-                    COALESCE(e.event_id, e_by_stream.event_id) AS event_id,
+                    e.event_id,
                     s.prev_event_id,
                     s.room_id,
-                    s.instance_name,
+                    COALESCE(e.instance_name, s.instance_name),
-                    COALESCE(e.stream_ordering, e_by_stream.stream_ordering, s.stream_id) AS stream_ordering,
+                    COALESCE(e.stream_ordering, s.stream_id),
-                    COALESCE(m.membership, m_by_stream.membership) AS membership,
+                    m.membership,
-                    COALESCE(e.sender, e_by_stream.sender) AS sender,
+                    e.sender
-                    m_prev.membership AS prev_membership
                 FROM current_state_delta_stream AS s
                     LEFT JOIN events AS e ON e.event_id = s.event_id
                     LEFT JOIN room_memberships AS m ON m.event_id = s.event_id
-                    LEFT JOIN room_memberships AS m_prev ON s.prev_event_id = m_prev.event_id
-                    LEFT JOIN events AS e_by_stream ON e_by_stream.stream_ordering = s.stream_id
-                        AND e_by_stream.type = ?
-                        AND e_by_stream.state_key = ?
-                    LEFT JOIN room_memberships AS m_by_stream ON m_by_stream.event_stream_ordering = s.stream_id
-                        AND m_by_stream.user_id = ?
                 WHERE s.stream_id > ? AND s.stream_id <= ?
-                    AND s.type = ?
                     AND s.state_key = ?
+                    AND s.type = ?
                 ORDER BY s.stream_id ASC
             """
 
             txn.execute(sql, args)
 
             membership_changes: List[CurrentStateDeltaMembership] = []
+            membership_change_map: Dict[str, CurrentStateDeltaMembership] = {}
             for (
                 event_id,
                 prev_event_id,
@@ -916,7 +899,6 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                 stream_ordering,
                 membership,
                 sender,
-                prev_membership,
             ) in txn:
                 assert room_id is not None
                 assert instance_name is not None
@@ -932,17 +914,21 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                     # `event_id = null` for all current state. This means we might
                     # already have a row for the leave event and then another for the
                     # same leave where the `event_id=null` but the `prev_event_id` is
-                    # pointing back at the earlier leave event. We don't want to report
+                    # pointing back at the earlier leave event. Since we're assuming the
-                    # the leave, if we already have a leave event.
+                    # `event_id = null` row is a `leave` and we don't want duplicate
-                    if event_id is None and prev_membership == Membership.LEAVE:
+                    # membership changes in our results, let's get rid of those
+                    # (deduplicate) (see `test_server_left_after_us_room`).
+                    if event_id is None:
+                        already_tracked_membership_change = membership_change_map.get(
+                            prev_event_id
+                        )
+                        if (
+                            already_tracked_membership_change is not None
+                            and already_tracked_membership_change.membership
+                            == Membership.LEAVE
+                        ):
                             continue
 
-                    # We can detect a state reset if there was a membership change
-                    # without a corresponding event.
-                    state_reset = False
-                    if event_id is None and membership != prev_membership:
-                        state_reset = True
-
                     membership_change = CurrentStateDeltaMembership(
                         event_id=event_id,
                         event_pos=PersistedEventPosition(
@@ -955,10 +941,11 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                             membership if membership is not None else Membership.LEAVE
                         ),
                         sender=sender,
-                        state_reset=state_reset,
                     )
 
                     membership_changes.append(membership_change)
+                    if event_id:
+                        membership_change_map[event_id] = membership_change
 
             return membership_changes
 

tests/storage/test_stream.py

@@ -615,7 +615,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 )
             ],
         )
@@ -717,7 +716,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 ),
                 CurrentStateDeltaMembership(
                     event_id=leave_response1["event_id"],
@@ -726,7 +724,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="leave",
                     sender=user1_id,
-                    state_reset=False,
                 ),
             ],
         )
@@ -788,9 +785,9 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
 
     def test_we_cause_server_left_room(self) -> None:
         """
-        Test that when probing over part of the DAG where the user leaves the room
+        Test that when probing over part of the DAG where we leave the room causing the
-        causing the server to leave the room (because we were the last local user in the
+        server to leave the room (because we were the last local user in the room), we
-        room), we still see the join and leave changes.
+        still see the join and leave changes.
 
         This is to make sure we play nicely with this behavior: When the server leaves a
         room, it will insert new rows with `event_id = null` into the
@@ -885,16 +882,14 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 ),
                 CurrentStateDeltaMembership(
-                    event_id=leave_response1["event_id"],
+                    event_id=None,  # leave_response1["event_id"],
                     event_pos=leave_pos1,
                     prev_event_id=join_response1["event_id"],
                     room_id=room_id1,
                     membership="leave",
-                    sender=user1_id,
+                    sender=None,  # user1_id,
-                    state_reset=False,
                 ),
             ],
         )
@@ -1009,7 +1004,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="join",
                     sender=user3_id,
-                    state_reset=False,
                 ),
             ],
         )
@@ -1025,7 +1019,7 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
         user2_tok = self.login(user2_id, "pass")
 
         room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
-        join_response1 = self.helper.join(room_id1, user1_id, tok=user1_tok)
+        self.helper.join(room_id1, user1_id, tok=user1_tok)
 
         before_reset_token = self.event_sources.get_current_token()
 
@@ -1062,7 +1056,8 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     "type": EventTypes.Member,
                     "state_key": user1_id,
                     "event_id": None,
-                    "prev_event_id": join_response1["event_id"],
+                    # FIXME: I'm not sure if a state reset should have a prev_event_id
+                    "prev_event_id": None,
                     "instance_name": dummy_state_pos.instance_name,
                 },
                 desc="state reset user in current_state_delta_stream",
@@ -1093,11 +1088,10 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                 CurrentStateDeltaMembership(
                     event_id=None,
                     event_pos=dummy_state_pos,
-                    prev_event_id=join_response1["event_id"],
+                    prev_event_id=None,
                     room_id=room_id1,
                     membership="leave",
                     sender=None,  # user1_id,
-                    state_reset=True,
                 ),
             ],
         )
@@ -1148,7 +1142,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 ),
                 CurrentStateDeltaMembership(
                     event_id=join_response2["event_id"],
@@ -1157,7 +1150,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id2,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 ),
             ],
         )
@@ -1184,7 +1176,6 @@ class GetCurrentStateDeltaMembershipChangesForUserTestCase(HomeserverTestCase):
                     room_id=room_id1,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 )
             ],
         )
@@ -1378,7 +1369,6 @@ class GetCurrentStateDeltaMembershipChangesForUserFederationTestCase(
                     room_id=intially_unjoined_room_id,
                     membership="join",
                     sender=user1_id,
-                    state_reset=False,
                 ),
             ],
         )