Allow room initialSync for users that have left the room, returning a snapshot of how the room was when they left it

1 files changed, 15 insertions, 0 deletions

diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index d7fe423f5a..0abfa86cd2 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -379,6 +379,21 @@ class StreamStore(SQLBaseStore):
             )
             defer.returnValue("t%d-%d" % (topo, token))
 
+    def get_stream_token_for_event(self, event_id):
+        """The stream token for an event
+        Args:
+            event_id(str): The id of the event to look up a stream token for.
+        Raises:
+            StoreError if the event wasn't in the database.
+        Returns:
+            A deferred "s%d" stream token.
+        """
+        return self._simple_select_one_onecol(
+            table="events",
+            keyvalues={"event_id": event_id},
+            retcol="stream_ordering",
+        ).addCallback(lambda stream_ordering: "s%d" % (stream_ordering,))
+
     def _get_max_topological_txn(self, txn):
         txn.execute(
             "SELECT MAX(topological_ordering) FROM events"