{
   head:{
        type:"APACHE_DRILL_PHYSICAL",
        version:"1",
        generator:{
            type:"manual"
        }
    },
    graph:[
        {
            @id:1,
            pop:"mock-sub-scan",
            url: "http://apache.org",
            entries:[
                {records: 1, types: [
                  {name: "varcharcol", type: "VARCHAR", mode: "REQUIRED"},
                  {name: "nullvarcharcol", type: "VARCHAR", mode: "OPTIONAL"}
                ]}
            ]
        },
        {
            @id:2,
            child: 1,
            pop:"project",
            exprs: [
              { ref: "col1", expr: "substring('abcdef', 1, 3)"},
              { ref: "col2", expr: "substring('abcdef', 2, 3)"},
              { ref: "col3", expr: "substring('abcdef', 2, 5)"},
              { ref: "col4", expr: "substring('abcdef', 2, 10)"},
              { ref: "col5", expr: "substring('abcdef', 0, 3)"},
              { ref: "col6", expr: "substring('abcdef', -1, 3)"},
              { ref: "col7", expr: "substring('', 1, 2)"},
              { ref: "col8", expr: "substring('abcdef', 10, 2)"},
              { ref: "col9", expr: "substring('भारतवर्ष', 1, 4)"},
              { ref: "col10", expr: "substring('भारतवर्ष', 5, 4)"},
              { ref: "col11", expr: "substring('भारतवर्ष', 5, 5)"},
              { ref: "col12", expr: "substring('abcdef', 3)"},
              { ref: "col13", expr: "substring('abcdef', -2)"},
              { ref: "col14", expr: "substring('abcdef', 0)"},
              { ref: "col15", expr: "substring('abcdef', 10)"},
              { ref: "col16", expr: "substring('अपाचे ड्रिल', 7)"}
            ]
        },
        {
            @id: 3,
            child: 2,
            pop: "screen"
        }
    ]
}