Support pagination tokens from /sync and /messages in the relations API. (#11952)

Author: clokep

changelog.d/11952.bugfix

@@ -0,0 +1 @@
+Fix a long-standing bug where pagination tokens from `/sync` and `/messages` could not be provided to the `/relations` API.

synapse/rest/client/relations.py

@@ -32,14 +32,45 @@
     PaginationChunk,
     RelationPaginationToken,
 )
-from synapse.types import JsonDict
+from synapse.types import JsonDict, RoomStreamToken, StreamToken
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
+    from synapse.storage.databases.main import DataStore
 
 logger = logging.getLogger(__name__)
 
 
+async def _parse_token(
+    store: "DataStore", token: Optional[str]
+) -> Optional[StreamToken]:
+    """
+    For backwards compatibility support RelationPaginationToken, but new pagination
+    tokens are generated as full StreamTokens, to be compatible with /sync and /messages.
+    """
+    if not token:
+        return None
+    # Luckily the format for StreamToken and RelationPaginationToken differ enough
+    # that they can easily be separated. An "_" appears in the serialization of
+    # RoomStreamToken (as part of StreamToken), but RelationPaginationToken uses
+    # "-" only for separators.
+    if "_" in token:
+        return await StreamToken.from_string(store, token)
+    else:
+        relation_token = RelationPaginationToken.from_string(token)
+        return StreamToken(
+            room_key=RoomStreamToken(relation_token.topological, relation_token.stream),
+            presence_key=0,
+            typing_key=0,
+            receipt_key=0,
+            account_data_key=0,
+            push_rules_key=0,
+            to_device_key=0,
+            device_list_key=0,
+            groups_key=0,
+        )
+
+
 class RelationPaginationServlet(RestServlet):
     """API to paginate relations on an event by topological ordering, optionally
     filtered by relation type and event type.
@@ -88,13 +119,8 @@ async def on_GET(
             pagination_chunk = PaginationChunk(chunk=[])
         else:
             # Return the relations
-            from_token = None
-            if from_token_str:
-                from_token = RelationPaginationToken.from_string(from_token_str)
-
-            to_token = None
-            if to_token_str:
-                to_token = RelationPaginationToken.from_string(to_token_str)
+            from_token = await _parse_token(self.store, from_token_str)
+            to_token = await _parse_token(self.store, to_token_str)
 
             pagination_chunk = await self.store.get_relations_for_event(
                 event_id=parent_id,
@@ -125,7 +151,7 @@ async def on_GET(
             events, now, bundle_aggregations=aggregations
         )
 
-        return_value = pagination_chunk.to_dict()
+        return_value = await pagination_chunk.to_dict(self.store)
         return_value["chunk"] = serialized_events
         return_value["original_event"] = original_event
 
@@ -216,7 +242,7 @@ async def on_GET(
                 to_token=to_token,
             )
 
-        return 200, pagination_chunk.to_dict()
+        return 200, await pagination_chunk.to_dict(self.store)
 
 
 class RelationAggregationGroupPaginationServlet(RestServlet):
@@ -287,13 +313,8 @@ async def on_GET(
         from_token_str = parse_string(request, "from")
         to_token_str = parse_string(request, "to")
 
-        from_token = None
-        if from_token_str:
-            from_token = RelationPaginationToken.from_string(from_token_str)
-
-        to_token = None
-        if to_token_str:
-            to_token = RelationPaginationToken.from_string(to_token_str)
+        from_token = await _parse_token(self.store, from_token_str)
+        to_token = await _parse_token(self.store, to_token_str)
 
         result = await self.store.get_relations_for_event(
             event_id=parent_id,
@@ -313,7 +334,7 @@ async def on_GET(
         now = self.clock.time_msec()
         serialized_events = self._event_serializer.serialize_events(events, now)
 
-        return_value = result.to_dict()
+        return_value = await result.to_dict(self.store)
         return_value["chunk"] = serialized_events
 
         return 200, return_value

synapse/storage/databases/main/relations.py

@@ -39,16 +39,13 @@
 )
 from synapse.storage.databases.main.stream import generate_pagination_where_clause
 from synapse.storage.engines import PostgresEngine
-from synapse.storage.relations import (
-    AggregationPaginationToken,
-    PaginationChunk,
-    RelationPaginationToken,
-)
-from synapse.types import JsonDict
+from synapse.storage.relations import AggregationPaginationToken, PaginationChunk
+from synapse.types import JsonDict, RoomStreamToken, StreamToken
 from synapse.util.caches.descriptors import cached, cachedList
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
+    from synapse.storage.databases.main import DataStore
 
 logger = logging.getLogger(__name__)
 
@@ -98,8 +95,8 @@ async def get_relations_for_event(
         aggregation_key: Optional[str] = None,
         limit: int = 5,
         direction: str = "b",
-        from_token: Optional[RelationPaginationToken] = None,
-        to_token: Optional[RelationPaginationToken] = None,
+        from_token: Optional[StreamToken] = None,
+        to_token: Optional[StreamToken] = None,
     ) -> PaginationChunk:
         """Get a list of relations for an event, ordered by topological ordering.
 
@@ -138,8 +135,10 @@ async def get_relations_for_event(
         pagination_clause = generate_pagination_where_clause(
             direction=direction,
             column_names=("topological_ordering", "stream_ordering"),
-            from_token=attr.astuple(from_token) if from_token else None,  # type: ignore[arg-type]
-            to_token=attr.astuple(to_token) if to_token else None,  # type: ignore[arg-type]
+            from_token=from_token.room_key.as_historical_tuple()
+            if from_token
+            else None,
+            to_token=to_token.room_key.as_historical_tuple() if to_token else None,
             engine=self.database_engine,
         )
 
@@ -177,12 +176,27 @@ def _get_recent_references_for_event_txn(
                 last_topo_id = row[1]
                 last_stream_id = row[2]
 
-            next_batch = None
+            # If there are more events, generate the next pagination key.
+            next_token = None
             if len(events) > limit and last_topo_id and last_stream_id:
-                next_batch = RelationPaginationToken(last_topo_id, last_stream_id)
+                next_key = RoomStreamToken(last_topo_id, last_stream_id)
+                if from_token:
+                    next_token = from_token.copy_and_replace("room_key", next_key)
+                else:
+                    next_token = StreamToken(
+                        room_key=next_key,
+                        presence_key=0,
+                        typing_key=0,
+                        receipt_key=0,
+                        account_data_key=0,
+                        push_rules_key=0,
+                        to_device_key=0,
+                        device_list_key=0,
+                        groups_key=0,
+                    )
 
             return PaginationChunk(
-                chunk=list(events[:limit]), next_batch=next_batch, prev_batch=from_token
+                chunk=list(events[:limit]), next_batch=next_token, prev_batch=from_token
             )
 
         return await self.db_pool.runInteraction(
@@ -676,13 +690,15 @@ async def _get_bundled_aggregation_for_event(
 
         annotations = await self.get_aggregation_groups_for_event(event_id, room_id)
         if annotations.chunk:
-            aggregations.annotations = annotations.to_dict()
+            aggregations.annotations = await annotations.to_dict(
+                cast("DataStore", self)
+            )
 
         references = await self.get_relations_for_event(
             event_id, room_id, RelationTypes.REFERENCE, direction="f"
         )
         if references.chunk:
-            aggregations.references = references.to_dict()
+            aggregations.references = await references.to_dict(cast("DataStore", self))
 
         # If this event is the start of a thread, include a summary of the replies.
         if self._msc3440_enabled:

synapse/storage/relations.py

@@ -13,13 +13,16 @@
 # limitations under the License.
 
 import logging
-from typing import Any, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple
 
 import attr
 
 from synapse.api.errors import SynapseError
 from synapse.types import JsonDict
 
+if TYPE_CHECKING:
+    from synapse.storage.databases.main import DataStore
+
 logger = logging.getLogger(__name__)
 
 
@@ -39,14 +42,14 @@ class PaginationChunk:
     next_batch: Optional[Any] = None
     prev_batch: Optional[Any] = None
 
-    def to_dict(self) -> Dict[str, Any]:
+    async def to_dict(self, store: "DataStore") -> Dict[str, Any]:
         d = {"chunk": self.chunk}
 
         if self.next_batch:
-            d["next_batch"] = self.next_batch.to_string()
+            d["next_batch"] = await self.next_batch.to_string(store)
 
         if self.prev_batch:
-            d["prev_batch"] = self.prev_batch.to_string()
+            d["prev_batch"] = await self.prev_batch.to_string(store)
 
         return d
 
@@ -75,7 +78,7 @@ def from_string(string: str) -> "RelationPaginationToken":
         except ValueError:
             raise SynapseError(400, "Invalid relation pagination token")
 
-    def to_string(self) -> str:
+    async def to_string(self, store: "DataStore") -> str:
         return "%d-%d" % (self.topological, self.stream)
 
     def as_tuple(self) -> Tuple[Any, ...]:
@@ -105,7 +108,7 @@ def from_string(string: str) -> "AggregationPaginationToken":
         except ValueError:
             raise SynapseError(400, "Invalid aggregation pagination token")
 
-    def to_string(self) -> str:
+    async def to_string(self, store: "DataStore") -> str:
         return "%d-%d" % (self.count, self.stream)
 
     def as_tuple(self) -> Tuple[Any, ...]: