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. 

zkutil::ZooKeeper & zookeeper, const String & partition_id, ContextPtr query_context, bool detach)
{
    Strings partition_ids = {partition_id};
    std::vector<LogEntryPtr> entries;
    dropAllPartsInPartitions(zookeeper, partition_ids, entries, query_context, detach);
    if (entries.empty())
        return {};
    return entries[0];
}
void StorageReplicatedMergeTree::enqueuePartForCheck(const String & part_name, time_t delay_to_check_seconds)
{
    MergeTreePartInfo covering_drop_range;
    if (queue.hasDropRange(MergeTreePartInfo::fromPartName(part_name, format_version), &covering_drop_range))
    {
        LOG_WARNING(log, "Do not enqueue part {} for check because it's covered by DROP_RANGE {} and going to be removed",
                    part_name, covering_drop_range.getPartName());
        return;
    }
    part_check_thread.enqueuePart(part_name, delay_to_check_seconds);
}
CheckResults StorageReplicatedMergeTree::checkData(const ASTPtr & query, ContextPtr local_context)