graph/db: gracefully handle duplicate channel policy announcements

graph/db/graph_test.go

@@ -944,6 +944,13 @@ func TestEdgePolicyCRUD(t *testing.T) {
 		require.NoError(t, graph.UpdateEdgePolicy(ctx, edge1))
 		require.NoError(t, graph.UpdateEdgePolicy(ctx, edge2))
 
+		// Even though we assert at the DB level that any newer edge
+		// update has a newer timestamp, we need to still gracefully
+		// handle the case where the same exact policy is re-added since
+		// it could be possible that our batch executor has two of the
+		// same policy updates in the same batch.
+		require.NoError(t, graph.UpdateEdgePolicy(ctx, edge1))
+
 		// Use the ForEachChannel method to fetch the policies and
 		// assert that the deserialized policies match the original
 		// ones.

graph/db/sql_store.go

@@ -780,7 +780,15 @@ func (s *SQLStore) UpdateEdgePolicy(ctx context.Context,
 			from, to, isUpdate1, err = updateChanEdgePolicy(
 				ctx, tx, edge,
 			)
-			if err != nil {
+			// It is possible that two of the same policy
+			// announcements are both being processed in the same
+			// batch. This may case the UpsertEdgePolicy conflict to
+			// be hit since we require at the db layer that the
+			// new last_update is greater than the existing
+			// last_update. We need to gracefully handle this here.
+			if errors.Is(err, sql.ErrNoRows) {
+				return nil
+			} else if err != nil {
 				log.Errorf("UpdateEdgePolicy faild: %v", err)
 			}