presto-main/src/main/java/io/prestosql/operator/JoinBridgeManager.java/TaskWideInternalJoinBridgeDataManager/getOuterPositionsFuture
class TaskWideInternalJoinBridgeDataManager:        @Override
        public ListenableFuture<OuterPositionIterator> getOuterPositionsFuture(Lifespan lifespan)
        {
            checkArgument(Lifespan.taskWide().equals(lifespan));
            return transform(joinLifecycle.whenBuildAndProbeFinishes(), ignored -> joinBridge.getOuterPositionIterator(), directExecutor());
        }