Allow paginating backwards from stream token

1 files changed, 14 insertions, 2 deletions

diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index 28721e6994..5096b46864 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -234,10 +234,10 @@ class StreamStore(SQLBaseStore):
                 get_prev_content=True
             )
 
-            ret.reverse()
-
             self._set_before_and_after(ret, rows, topo_order=False)
 
+            ret.reverse()
+
             if rows:
                 key = "s%d" % min(r["stream_ordering"] for r in rows)
             else:
@@ -570,6 +570,18 @@ class StreamStore(SQLBaseStore):
             row["topological_ordering"], row["stream_ordering"],)
         )
 
+    def get_max_topological_token_for_stream_and_room(self, room_id, stream_key):
+        sql = (
+            "SELECT max(topological_ordering) FROM events"
+            " WHERE room_id = ? AND stream_ordering < ?"
+        )
+        return self._execute(
+            "get_max_topological_token_for_stream_and_room", None,
+            sql, room_id, stream_key,
+        ).addCallback(
+            lambda r: r[0][0] if r else 0
+        )
+
     def _get_max_topological_txn(self, txn):
         txn.execute(
             "SELECT MAX(topological_ordering) FROM events"