presto-main/src/main/java/io/prestosql/operator/NestedLoopJoinOperator.java/NestedLoopJoinOperator/isFinished
class NestedLoopJoinOperator:    @Override
    public boolean isFinished()
    {
        boolean finished = finishing && probePage == null;

        if (finished) {
            close();
        }
        return finished;
    }