presto-main/src/main/java/io/prestosql/operator/exchange/LocalExchange.java/LocalExchange/noMoreSinkFactories
class LocalExchange:    private void noMoreSinkFactories()
    {
        checkNotHoldsLock(this);

        synchronized (this) {
            noMoreSinkFactories = true;
        }
        checkAllSinksComplete();
    }