```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
```
{
    for (auto & stream : streams)
        stream->getProcessor().enableQuota();
}
void QueryPipeline::addTotalsHavingTransform(ProcessorPtr transform)
{
    checkInitializedAndNotCompleted();
    if (!typeid_cast<const TotalsHavingTransform *>(transform.get()))
        throw Exception("TotalsHavingTransform expected for QueryPipeline::addTotalsHavingTransform.",
                ErrorCodes::LOGICAL_ERROR);
    if (totals_having_port)
        throw Exception("Totals having transform was already added to pipeline.", ErrorCodes::LOGICAL_ERROR);
    resize(1);
    connect(*streams.front(), transform->getInputs().front());
    auto & outputs = transform->getOutputs();
    streams.assign({ &outputs.front() });
    totals_having_port = &outputs.back();
    current_header = outputs.front().getHeader();
    processors.emplace(std::move(transform));
}
void QueryPipeline::addDefaultTotals()