Use upsert for receipts_graph.

changelog.d/13752.misc

@@ -0,0 +1 @@
+User an additional database query when persisting receipts.

synapse/storage/databases/main/receipts.py

@@ -812,25 +812,21 @@ def _insert_graph_receipt_txn(
         # FIXME: This shouldn't invalidate the whole cache
         txn.call_after(self._get_linearized_receipts_for_room.invalidate, (room_id,))
 
-        self.db_pool.simple_delete_txn(
+        self.db_pool.simple_upsert_txn(
             txn,
             table="receipts_graph",
             keyvalues={
                 "room_id": room_id,
                 "receipt_type": receipt_type,
                 "user_id": user_id,
             },
-        )
-        self.db_pool.simple_insert_txn(
-            txn,
-            table="receipts_graph",
             values={
-                "room_id": room_id,
-                "receipt_type": receipt_type,
-                "user_id": user_id,
                 "event_ids": json_encoder.encode(event_ids),
                 "data": json_encoder.encode(data),
             },
+            # receipts_graph has a unique constraint on
+            # (user_id, room_id, receipt_type), so no need to lock
+            lock=False,
         )