presto-main/src/main/java/io/prestosql/execution/scheduler/AllAtOnceExecutionSchedule.java/Visitor/visitRemoteSource
class Visitor:        @Override
        public Void visitRemoteSource(RemoteSourceNode node, Void context)
        {
            node.getSourceFragmentIds()
                    .forEach(this::processFragment);
            return null;
        }