Advertise MSC4445 sync timeline order

[MadLittleMods]

Advertise MSC4445 sync timeline order

Synapse uses topological ordering for initial sync (first time a room is sent down /sync)

synapse/synapse/handlers/sync.py

Lines 768 to 805 in 2e9b820

	# For initial `/sync`, 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 since_key is None
	# Use `stream_ordering` for updates
	else paginate_room_events_by_stream_ordering
	)
	events, end_key, limited = 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.
	# This ensures we fill the `limit` with the newest events first,
	from_key=end_key,
	to_key=since_key,
	direction=Direction.BACKWARDS,
	limit=load_limit,
	)

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Code style is correct (run the linters)

[MadLittleMods]

Thanks for the review @erikjohnston 🐠