presto-main/src/main/java/io/prestosql/execution/scheduler/SourcePartitionedScheduler.java/SourcePartitionedScheduler/startLifespan
class SourcePartitionedScheduler:    @Override
    public synchronized void startLifespan(Lifespan lifespan, ConnectorPartitionHandle partitionHandle)
    {
        checkState(state == State.INITIALIZED || state == State.SPLITS_ADDED);
        scheduleGroups.put(lifespan, new ScheduleGroup(partitionHandle));
        whenFinishedOrNewLifespanAdded.set(null);
        whenFinishedOrNewLifespanAdded = SettableFuture.create();
    }