presto-main/src/main/java/io/prestosql/operator/LookupJoinOperator.java/LookupJoinOperator/needsInput
class LookupJoinOperator:    @Override
    public boolean needsInput()
    {
        return joinProcessor.lookupSourceProviderFuture.isDone() && pageBuffer.isEmpty() && !pageBuffer.isFinished();
    }