```sql
SELECT count()
FROM 
(
    SELECT number
    FROM numbers_mt(100000000)
    ORDER BY number DESC
    LIMIT 100
    UNION ALL
    SELECT number
    FROM numbers_mt(100000000)
    ORDER BY number DESC
    LIMIT 100
    UNION ALL
    SELECT number
    FROM numbers_mt(100000000)
    ORDER BY number DESC
    LIMIT 100
)


SET experimental_use_processors = 0;
-- 1 rows in set. Elapsed: 1.581 sec. Processed 300.00 million rows, 2.40 GB (189.78 million rows/s., 1.52 GB/s.) 

SET experimental_use_processors = 1;
-- 1 rows in set. Elapsed: 3.569 sec. Processed 300.00 million rows, 2.40 GB (84.06 million rows/s., 672.50 MB/s.) 
```

Similar for MergeTree:

```sql
create table test engine=MergeTree order by tuple() as select * from numbers(30000000);

select count() from (select number from test group by number order by number limit 10 union all select number from test group by number order by number limit 10);

set experimental_use_processors=0;
-- Elapsed: 2.664 sec

set experimental_use_processors=1;
-- Elapsed: 3.656 sec
```
{
    checkInitializedAndNotCompleted();
    if (extremes_port)
        throw Exception("Extremes transform was already added to pipeline.", ErrorCodes::LOGICAL_ERROR);
    std::vector<OutputPort *> extremes;
    extremes.reserve(streams.size());
    for (auto & stream : streams)
    {
        auto transform = std::make_shared<ExtremesTransform>(current_header);
        connect(*stream, transform->getInputPort());
        stream = &transform->getOutputPort();
        extremes.push_back(&transform->getExtremesPort());
        processors.emplace(std::move(transform));
    }
    if (extremes.size() == 1)
        extremes_port = extremes.front();
    else
        extremes_port = uniteExtremes(extremes, current_header, processors);
}
void QueryPipeline::addCreatingSetsTransform(ProcessorPtr transform)