{
    "_yql_row_spec"={
        "Type"=["StructType";[
            ["k";["OptionalType";["DataType";"String"]]];
            ["val";["OptionalType";["DataType";"String"]]]]
        ];
    };

    "schema" = <"strict" = %true; "unique_keys" = %false>
    [
        {
            "name" = "k";
            "type" = "string";
            "type_v3" = {"type_name" = "optional"; item = "string"}
        };
        {
            "name" = "val";
            "type" = "string";
            "type_v3" = {"type_name" = "optional"; item = "string"}
        };
    ];
    "extended_stats" = [
        {
            "column_name" = "k";
            "data_weight" = 18;
            "num_unique_vals" = 2;
        };
        {
            "column_name" = "val";
            "data_weight" = 20;
            "num_unique_vals" = 3;
        }
    ]
}