diff --git a/synapse/handlers/sliding_sync.py b/synapse/handlers/sliding_sync.py
index 1db96ad41c..0fe66c8bd2 100644
--- a/synapse/handlers/sliding_sync.py
+++ b/synapse/handlers/sliding_sync.py
@@ -64,7 +64,10 @@ from synapse.storage.databases.main.state import (
ROOM_UNKNOWN_SENTINEL,
Sentinel as StateSentinel,
)
-from synapse.storage.databases.main.stream import CurrentStateDeltaMembership
+from synapse.storage.databases.main.stream import (
+ CurrentStateDeltaMembership,
+ PaginateFunction,
+)
from synapse.storage.roommember import MemberSummary
from synapse.types import (
DeviceListUpdates,
@@ -1863,10 +1866,13 @@ class SlidingSyncHandler:
# We should return historical messages (before token range) in the
# following cases because we want clients to be able to show a basic
# screen of information:
+ #
# - Initial sync (because no `from_token` to limit us anyway)
# - When users `newly_joined`
# - For an incremental sync where we haven't sent it down this
# connection before
+ #
+ # Relevant spec issue: https://github.com/matrix-org/matrix-spec/issues/1917
from_bound = None
initial = True
if from_token and not room_membership_for_user_at_to_token.newly_joined:
@@ -1927,7 +1933,36 @@ class SlidingSyncHandler:
room_membership_for_user_at_to_token.event_pos.to_room_stream_token()
)
- timeline_events, new_room_key = await self.store.paginate_room_events(
+ # For initial `/sync` (and other historical scenarios mentioned above), we
+ # want to view a historical section of the timeline; to fetch events by
+ # `topological_ordering` (best representation of the room DAG as others were
+ # seeing it at the time). This also aligns with the order that `/messages`
+ # returns events in.
+ #
+ # For incremental `/sync`, we want to get all updates for rooms since
+ # the last `/sync` (regardless if those updates arrived late or happened
+ # a while ago in the past); to fetch events by `stream_ordering` (in the
+ # order they were received by the server).
+ #
+ # Relevant spec issue: https://github.com/matrix-org/matrix-spec/issues/1917
+ #
+ # FIXME: Using workaround for mypy,
+ # https://github.com/python/mypy/issues/10740#issuecomment-1997047277 and
+ # https://github.com/python/mypy/issues/17479
+ paginate_room_events_by_topological_ordering: PaginateFunction = (
+ self.store.paginate_room_events_by_topological_ordering
+ )
+ paginate_room_events_by_stream_ordering: PaginateFunction = (
+ self.store.paginate_room_events_by_stream_ordering
+ )
+ pagination_method: PaginateFunction = (
+ # Use `topographical_ordering` for historical events
+ paginate_room_events_by_topological_ordering
+ if from_bound is None
+ # Use `stream_ordering` for updates
+ else paginate_room_events_by_stream_ordering
+ )
+ timeline_events, new_room_key = await pagination_method(
room_id=room_id,
# The bounds are reversed so we can paginate backwards
# (from newer to older events) starting at to_bound.
@@ -1938,7 +1973,6 @@ class SlidingSyncHandler:
# We add one so we can determine if there are enough events to saturate
# the limit or not (see `limited`)
limit=room_sync_config.timeline_limit + 1,
- event_filter=None,
)
# We want to return the events in ascending order (the last event is the
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