{
    head:{
        type:"APACHE_DRILL_PHYSICAL",
        version:"1",
        generator:{
            type:"manual"
        }
    },
    graph:[
        {
            @id:1,
            pop:"mock-scan",
            url: "http://apache.org",
            entries:[
                {records: 1, types: [
                  {name: "col1", type: "FLOAT4", mode: "REQUIRED"},
                  {name: "col2", type: "FLOAT8", mode: "REQUIRED"}
             ]}
            ]
        },
        {
            @id:2,
            child: 1,
            pop:"project",
            exprs: [
            {ref: "str_to_int_cast", expr:"8 + '2'" },
            {ref: "int_to_str_cast", expr:"substr(10123, 1, 3)" }
            ]
        },
        {
            @id: 3,
            child: 2,
            pop: "screen"
        }
    ]
}