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. 

{
    if (indices.blocks.size() > num_indices_saved)
        indices.blocks.resize(num_indices_saved);
}
void StorageStripeLog::saveFileSizes(const WriteLock & )
{
    file_checker.update(data_file_path);
    file_checker.update(index_file_path);
    file_checker.save();
    total_bytes = file_checker.getTotalSize();
}
void StorageStripeLog::updateTotalRows(const WriteLock &)
{
    if (!indices_loaded)
        return;
    size_t new_total_rows = 0;
    for (const auto & block : indices.blocks)
        new_total_rows += block.num_rows;
    total_rows = new_total_rows;
}
std::optional<UInt64> StorageStripeLog::totalRows(const Settings &) const
{
    if (indices_loaded)
        return total_rows;
    if (!total_bytes)
        return 0;
    return {};
}
std::optional<UInt64> StorageStripeLog::totalBytes(const Settings &) const