Remove an unnecessary class from the relations code. (#12338)

The PaginationChunk class attempted to bundle some properties
together, but really just caused callers to jump through hoops and
hid implementation details.

synapse/storage/databases/main/relations.py

@@ -37,7 +37,6 @@ from synapse.storage.database import (
 )
 from synapse.storage.databases.main.stream import generate_pagination_where_clause
 from synapse.storage.engines import PostgresEngine
-from synapse.storage.relations import PaginationChunk
 from synapse.types import JsonDict, RoomStreamToken, StreamToken
 from synapse.util.caches.descriptors import cached, cachedList
 
@@ -71,7 +70,7 @@ class RelationsWorkerStore(SQLBaseStore):
         direction: str = "b",
         from_token: Optional[StreamToken] = None,
         to_token: Optional[StreamToken] = None,
-    ) -> PaginationChunk:
+    ) -> Tuple[List[str], Optional[StreamToken]]:
         """Get a list of relations for an event, ordered by topological ordering.
 
         Args:
@@ -88,8 +87,10 @@ class RelationsWorkerStore(SQLBaseStore):
             to_token: Fetch rows up to the given token, or up to the end if None.
 
         Returns:
-            List of event IDs that match relations requested. The rows are of
-            the form `{"event_id": "..."}`.
+            A tuple of:
+                A list of related event IDs
+
+                The next stream token, if one exists.
         """
         # We don't use `event_id`, it's there so that we can cache based on
         # it. The `event_id` must match the `event.event_id`.
@@ -144,7 +145,7 @@ class RelationsWorkerStore(SQLBaseStore):
 
         def _get_recent_references_for_event_txn(
             txn: LoggingTransaction,
-        ) -> PaginationChunk:
+        ) -> Tuple[List[str], Optional[StreamToken]]:
             txn.execute(sql, where_args + [limit + 1])
 
             last_topo_id = None
@@ -154,7 +155,7 @@ class RelationsWorkerStore(SQLBaseStore):
                 # Do not include edits for redacted events as they leak event
                 # content.
                 if not is_redacted or row[1] != RelationTypes.REPLACE:
-                    events.append({"event_id": row[0]})
+                    events.append(row[0])
                 last_topo_id = row[2]
                 last_stream_id = row[3]
 
@@ -177,9 +178,7 @@ class RelationsWorkerStore(SQLBaseStore):
                         groups_key=0,
                     )
 
-            return PaginationChunk(
-                chunk=list(events[:limit]), next_batch=next_token, prev_batch=from_token
-            )
+            return events[:limit], next_token
 
         return await self.db_pool.runInteraction(
             "get_recent_references_for_event", _get_recent_references_for_event_txn

synapse/storage/relations.py

@@ -1,53 +0,0 @@
-# Copyright 2019 New Vector Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import logging
-from typing import TYPE_CHECKING, Any, Dict, List, Optional
-
-import attr
-
-from synapse.types import JsonDict
-
-if TYPE_CHECKING:
-    from synapse.storage.databases.main import DataStore
-
-logger = logging.getLogger(__name__)
-
-
-@attr.s(slots=True, auto_attribs=True)
-class PaginationChunk:
-    """Returned by relation pagination APIs.
-
-    Attributes:
-        chunk: The rows returned by pagination
-        next_batch: Token to fetch next set of results with, if
-            None then there are no more results.
-        prev_batch: Token to fetch previous set of results with, if
-            None then there are no previous results.
-    """
-
-    chunk: List[JsonDict]
-    next_batch: Optional[Any] = None
-    prev_batch: Optional[Any] = None
-
-    async def to_dict(self, store: "DataStore") -> Dict[str, Any]:
-        d = {"chunk": self.chunk}
-
-        if self.next_batch:
-            d["next_batch"] = await self.next_batch.to_string(store)
-
-        if self.prev_batch:
-            d["prev_batch"] = await self.prev_batch.to_string(store)
-
-        return d