Verify ?chunk_id actually corresponds to an insertion event that exists (MSC2716) (#10776)

synapse/storage/databases/main/room_batch.py

@@ -0,0 +1,36 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+from typing import Optional
+
+from synapse.storage._base import SQLBaseStore
+
+
+class RoomBatchStore(SQLBaseStore):
+    async def get_insertion_event_by_chunk_id(self, chunk_id: str) -> Optional[str]:
+        """Retrieve a insertion event ID.
+
+        Args:
+            chunk_id: The chunk ID of the insertion event to retrieve.
+
+        Returns:
+            The event_id of an insertion event, or None if there is no known
+            insertion event for the given insertion event.
+        """
+        return await self.db_pool.simple_select_one_onecol(
+            table="insertion_events",
+            keyvalues={"next_chunk_id": chunk_id},
+            retcol="event_id",
+            allow_none=True,
+        )