And waits for them. That's pointless.
source_part_paths.emplace_back(source_part->getFullPath());
        total_size_bytes_compressed += source_part->getBytesOnDisk();
        total_size_marks += source_part->getMarksCount();
        total_rows_count += source_part->index_granularity.getTotalRows();
    }
    if (!future_part.parts.empty())
    {
        source_data_version = future_part.parts[0]->info.getDataVersion();
        is_mutation = (result_data_version != source_data_version);
    }
    
    background_thread_memory_tracker = CurrentThread::getMemoryTracker();
    if (background_thread_memory_tracker)
    {
        
        
        
        
        MemoryTracker * parent;
        if (background_thread_memory_tracker->level == VariableContext::Thread &&
            (parent = background_thread_memory_tracker->getParent()) &&
            parent != &total_memory_tracker)
        {
            background_thread_memory_tracker = parent;
        }
        background_thread_memory_tracker_prev_parent = background_thread_memory_tracker->getParent();
        background_thread_memory_tracker->setParent(&memory_tracker);
    }
}
MergeInfo MergeListElement::getInfo() const