Noop device key changes if they're the same

synapse/handlers/e2e_keys.py

@@ -287,11 +287,12 @@ class E2eKeysHandler(object):
                 device_id, user_id, time_now
             )
             # TODO: Sign the JSON with the server key
-            yield self.store.set_e2e_device_keys(
-                user_id, device_id, time_now,
-                encode_canonical_json(device_keys)
+            changed = yield self.store.set_e2e_device_keys(
+                user_id, device_id, time_now, device_keys,
             )
-            yield self.device_handler.notify_device_update(user_id, [device_id])
+            if changed:
+                # Only notify about device updates *if* the keys actually changed
+                yield self.device_handler.notify_device_update(user_id, [device_id])
 
         one_time_keys = keys.get("one_time_keys", None)
         if one_time_keys:

synapse/storage/devices.py

@@ -164,6 +164,7 @@ class DeviceStore(SQLBaseStore):
             keyvalues={
                 "user_id": user_id,
             },
+            desc="mark_remote_user_device_list_as_unsubscribed",
         )
 
     def update_remote_device_list_cache_entry(self, user_id, device_id, content,

synapse/storage/end_to_end_keys.py

@@ -14,21 +14,49 @@
 # limitations under the License.
 from twisted.internet import defer
 
+from canonicaljson import encode_canonical_json
+
 from ._base import SQLBaseStore
 
 
 class EndToEndKeyStore(SQLBaseStore):
-    def set_e2e_device_keys(self, user_id, device_id, time_now, json_bytes):
-        return self._simple_upsert(
-            table="e2e_device_keys_json",
-            keyvalues={
-                "user_id": user_id,
-                "device_id": device_id,
-            },
-            values={
-                "ts_added_ms": time_now,
-                "key_json": json_bytes,
-            }
+    def set_e2e_device_keys(self, user_id, device_id, time_now, device_keys):
+        """Stores device keys for a device. Returns whether there was a change
+        or the keys were already in the database.
+        """
+        def _set_e2e_device_keys_txn(txn):
+            old_key_json = self._simple_select_one_onecol_txn(
+                txn,
+                table="e2e_device_keys_json",
+                keyvalues={
+                    "user_id": user_id,
+                    "device_id": device_id,
+                },
+                retcol="key_json",
+                allow_none=True,
+            )
+
+            new_key_json = encode_canonical_json(device_keys)
+            if old_key_json == new_key_json:
+                return False
+
+            self._simple_upsert_txn(
+                txn,
+                table="e2e_device_keys_json",
+                keyvalues={
+                    "user_id": user_id,
+                    "device_id": device_id,
+                },
+                values={
+                    "ts_added_ms": time_now,
+                    "key_json": new_key_json,
+                }
+            )
+
+            return True
+
+        return self.runInteraction(
+            "set_e2e_device_keys", _set_e2e_device_keys_txn
         )
 
     def get_e2e_device_keys(self, query_list, include_all_devices=False):