Stop writing to event_reference_hashes (#12679)

This table is never read, since #11794. We stop writing to it; in future we can
drop it altogether.

changelog.d/12679.misc

@@ -0,0 +1 @@
+Preparation for database schema simplifications: stop writing to `event_reference_hashes`.

synapse/storage/databases/main/events.py

@@ -36,7 +36,6 @@
 import synapse.metrics
 from synapse.api.constants import EventContentFields, EventTypes, RelationTypes
 from synapse.api.room_versions import RoomVersions
-from synapse.crypto.event_signing import compute_event_reference_hash
 from synapse.events import EventBase  # noqa: F401
 from synapse.events.snapshot import EventContext  # noqa: F401
 from synapse.storage._base import db_to_json, make_in_list_sql_clause
@@ -1600,11 +1599,6 @@ def _update_metadata_tables_txn(
             inhibit_local_membership_updates=inhibit_local_membership_updates,
         )
 
-        # Insert event_reference_hashes table.
-        self._store_event_reference_hashes_txn(
-            txn, [event for event, _ in events_and_contexts]
-        )
-
         # Prefill the event cache
         self._add_to_cache(txn, events_and_contexts)
 
@@ -1704,25 +1698,6 @@ def _insert_event_expiry_txn(self, txn, event_id, expiry_ts):
             values={"event_id": event_id, "expiry_ts": expiry_ts},
         )
 
-    def _store_event_reference_hashes_txn(self, txn, events):
-        """Store a hash for a PDU
-        Args:
-            txn (cursor):
-            events (list): list of Events.
-        """
-
-        vals = []
-        for event in events:
-            ref_alg, ref_hash_bytes = compute_event_reference_hash(event)
-            vals.append((event.event_id, ref_alg, memoryview(ref_hash_bytes)))
-
-        self.db_pool.simple_insert_many_txn(
-            txn,
-            table="event_reference_hashes",
-            keys=("event_id", "algorithm", "hash"),
-            values=vals,
-        )
-
     def _store_room_members_txn(
         self, txn, events, *, inhibit_local_membership_updates: bool = False
     ):

synapse/storage/databases/main/purge_events.py

@@ -69,7 +69,6 @@ def _purge_history_txn(
         #     event_forward_extremities
         #     event_json
         #     event_push_actions
-        #     event_reference_hashes
         #     event_relations
         #     event_search
         #     event_to_state_groups
@@ -220,7 +219,6 @@ def _purge_history_txn(
             "event_auth",
             "event_edges",
             "event_forward_extremities",
-            "event_reference_hashes",
             "event_relations",
             "event_search",
             "rejections",
@@ -369,7 +367,6 @@ def _purge_room_txn(self, txn: LoggingTransaction, room_id: str) -> List[int]:
             "event_edges",
             "event_json",
             "event_push_actions_staging",
-            "event_reference_hashes",
             "event_relations",
             "event_to_state_groups",
             "event_auth_chains",

synapse/storage/schema/__init__.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-SCHEMA_VERSION = 69  # remember to update the list below when updating
+SCHEMA_VERSION = 70  # remember to update the list below when updating
 """Represents the expectations made by the codebase about the database schema
 
 This should be incremented whenever the codebase changes its requirements on the
@@ -62,6 +62,9 @@
 Changes in SCHEMA_VERSION = 69:
     - We now write to `device_lists_changes_in_room` table.
     - Use sequence to generate future `application_services_txns.txn_id`s
+
+Changes in SCHEMA_VERSION = 70:
+    - event_reference_hashes is no longer written to.
 """
 
 

tests/storage/test_event_federation.py

@@ -58,15 +58,6 @@ def insert_event(txn, i):
                 (room_id, event_id),
             )
 
-            txn.execute(
-                (
-                    "INSERT INTO event_reference_hashes "
-                    "(event_id, algorithm, hash) "
-                    "VALUES (?, 'sha256', ?)"
-                ),
-                (event_id, bytearray(b"ffff")),
-            )
-
         for i in range(0, 20):
             self.get_success(
                 self.store.db_pool.runInteraction("insert", insert_event, i)