**Use case**
mysql repl to clickhouse

**Describe the solution you'd like**
Hope MaterializeMySQL engine can support MySQL prefix index



{
    const auto & is_unique = [&](const String & column_name)
    {
        for (const auto & column_name_and_type : columns_name_and_type)
        {
            if (column_name_and_type.name == column_name)
                return false;
        }
        return true;
    };
    if (is_unique(prefix))
        return prefix;
    for (size_t index = 0; ; ++index)
    {
        const String & cur_name = prefix + "_" + toString(index);
        if (is_unique(cur_name))
            return cur_name;
    }
}
static ASTPtr getPartitionPolicy(const NamesAndTypesList & primary_keys)