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. 

{
public:
    static Block getHeader(
        const StorageSnapshotPtr & storage_snapshot,
        const Names & column_names,
        IndexForNativeFormat::Blocks::const_iterator index_begin,
        IndexForNativeFormat::Blocks::const_iterator index_end)
    {
        if (index_begin == index_end)
            return storage_snapshot->getSampleBlockForColumns(column_names);
        
        Block header;
        for (const auto & column : index_begin->columns)
        {
            auto type = DataTypeFactory::instance().get(column.type);
            header.insert(ColumnWithTypeAndName{ type, column.name });
        }
        return header;
    }
    StripeLogSource(