Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

for (auto & part : parts_to_delete_completely)
    {
        if (!part_names_to_retry_deletion.contains(part->name))
            parts_to_remove_from_filesystem.emplace_back(part);
        else
            parts_to_retry_deletion.emplace_back(part);
    }
    
    if (!parts_to_retry_deletion.empty())
    {
        rollbackDeletingParts(parts_to_retry_deletion);
        LOG_DEBUG(log, "Will retry deletion of {} parts in the next time", parts_to_retry_deletion.size());
    }
    
    if (!parts_to_remove_from_filesystem.empty())
    {
        
        
        
        delete_parts_from_fs_and_rollback_in_case_of_error(parts_to_remove_from_filesystem, "old");
    }
}
void StorageReplicatedMergeTree::removePartsFromZooKeeperWithRetries(DataPartsVector & parts, size_t max_retries)
{
    Strings part_names_to_remove;
    for (const auto & part : parts)
        part_names_to_remove.emplace_back(part->name);
    return removePartsFromZooKeeperWithRetries(part_names_to_remove, max_retries);
}
void StorageReplicatedMergeTree::removePartsFromZooKeeperWithRetries(const Strings & part_names, size_t max_retries)