Listing all parts in log have no sense. 
Should be either silenced, either combined into a single line.
std::vector<QueryPlanPtr> partition_plans;
    
    
    std::vector<RangesInDataPart> lonely_parts;
    size_t total_rows_in_lonely_parts = 0;
    size_t sum_marks_in_lonely_parts = 0;
    for (size_t range_index = 0; range_index < parts_to_merge_ranges.size() - 1; ++range_index)
    {
        QueryPlanPtr plan;
        {
            Pipes pipes;
            
            
            
            
            if (num_streams > 1 && settings.do_not_merge_across_partitions_select_final &&
                std::distance(parts_to_merge_ranges[range_index], parts_to_merge_ranges[range_index + 1]) == 1 &&
                parts_to_merge_ranges[range_index]->data_part->info.level > 0)
            {
                total_rows_in_lonely_parts += parts_to_merge_ranges[range_index]->getRowsCount();
                sum_marks_in_lonely_parts += parts_to_merge_ranges[range_index]->getMarksCount();
                lonely_parts.push_back(std::move(*parts_to_merge_ranges[range_index]));
                continue;
            }
            else
            {
                for (auto part_it = parts_to_merge_ranges[range_index]; part_it != parts_to_merge_ranges[range_index + 1]; ++part_it)
                {
                    auto source_processor = std::make_shared<MergeTreeSelectProcessor>(
                        data,