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.

3 files changed, 4 insertions, 29 deletions

diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index ed29a0a5e2..ad611b2c0b 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -36,7 +36,6 @@ from prometheus_client import Counter
 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 @@ class PersistEventsStore:
             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 @@ class PersistEventsStore:
             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
     ):
diff --git a/synapse/storage/databases/main/purge_events.py b/synapse/storage/databases/main/purge_events.py
index bfc85b3add..38ba91af4c 100644
--- a/synapse/storage/databases/main/purge_events.py
+++ b/synapse/storage/databases/main/purge_events.py
@@ -69,7 +69,6 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
         #     event_forward_extremities
         #     event_json
         #     event_push_actions
-        #     event_reference_hashes
         #     event_relations
         #     event_search
         #     event_to_state_groups
@@ -220,7 +219,6 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
             "event_auth",
             "event_edges",
             "event_forward_extremities",
-            "event_reference_hashes",
             "event_relations",
             "event_search",
             "rejections",
@@ -369,7 +367,6 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
             "event_edges",
             "event_json",
             "event_push_actions_staging",
-            "event_reference_hashes",
             "event_relations",
             "event_to_state_groups",
             "event_auth_chains",
diff --git a/synapse/storage/schema/__init__.py b/synapse/storage/schema/__init__.py
index 871d4ace12..20c344faea 100644
--- a/synapse/storage/schema/__init__.py
+++ b/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 = 68:
 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.
 """