And waits for them. That's pointless.
if (auto disk = reserved_space->getDisk(); disk->getType() == DB::DiskType::Type::S3)
        {
            if (merge_strategy_picker.shouldMergeOnSingleReplicaS3Shared(entry))
            {
                if (!replica_to_execute_merge_picked)
                    replica_to_execute_merge = merge_strategy_picker.pickReplicaToExecuteMerge(entry);
                if (replica_to_execute_merge)
                {
                    LOG_DEBUG(log,
                        "Prefer fetching part {} from replica {} due s3_execute_merges_on_single_replica_time_threshold",
                        entry.new_part_name, replica_to_execute_merge.value());
                    return false;
                }
            }
        }
    }
    
    if (isTTLMergeType(future_merged_part.merge_type))
        getContext()->getMergeList().bookMergeWithTTL();
    auto table_id = getStorageID();
    
    MergeList::EntryPtr merge_entry = getContext()->getMergeList().insert(getStorageID(), future_merged_part);
    Transaction transaction(*this);
    MutableDataPartPtr part;
    Stopwatch stopwatch;
    auto write_part_log = [&] (const ExecutionStatus & execution_status)
    {
        writePartLog(
            PartLogElement::MERGE_PARTS, execution_status, stopwatch.elapsed(),
            entry.new_part_name, part, parts, merge_entry.get());