presto-main/src/main/java/io/prestosql/operator/JoinBridgeManager.java/JoinBridgeManager/getOuterPositionsFuture
class JoinBridgeManager:        @Override
        public ListenableFuture<OuterPositionIterator> getOuterPositionsFuture(Lifespan lifespan)
        {
            checkArgument(Lifespan.taskWide().equals(lifespan), "join bridge is not partitioned");
            return transform(joinLifecycle.whenBuildAndProbeFinishes(), ignored -> taskWideJoinBridge.getOuterPositionIterator(), directExecutor());
        }