Support pagination for tokens without chunk part

synapse/storage/stream.py

@@ -730,6 +730,30 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
         # ordered by stream_ordering column. If topological, then we need to
         # fetch events from one chunk at a time until we hit the limit.
 
+        # For backwards compatibility we need to check if the token has a
+        # topological part but no chunk part. If that's the case we can use the
+        # stream part to generate an appropriate topological token.
+        if from_token.chunk is None and from_token.topological is not None:
+            res = self._simple_select_one_txn(
+                txn,
+                table="events",
+                keyvalues={
+                    "stream_ordering": from_token.stream,
+                },
+                retcols=(
+                    "chunk_id",
+                    "topological_ordering",
+                    "stream_ordering",
+                ),
+                allow_none=True,
+            )
+            if res and res["chunk_id"] is not None:
+                from_token = RoomStreamToken(
+                    res["chunk_id"],
+                    res["topological_ordering"],
+                    res["stream_ordering"],
+                )
+
         # Tokens really represent positions between elements, but we use
         # the convention of pointing to the event before the gap. Hence
         # we have a bit of asymmetry when it comes to equalities.
@@ -783,11 +807,10 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
         iterated_chunks = []
 
         chunk_id = None
-        if from_token.chunk:  # FIXME: may be topological but no chunk.
         if rows:
             chunk_id = rows[-1].chunk_id
             iterated_chunks = [r.chunk_id for r in rows]
-            else:
+        elif from_token.chunk:
             chunk_id = from_token.chunk
             iterated_chunks = [chunk_id]