{
    head:{
        type:"APACHE_DRILL_PHYSICAL",
        version:"1",
        generator:{
            type:"manual"
        }
    },
  graph : [ {
    pop : "parquet-scan",
    @id : 1,
    entries : [ {
      path : "/tmp/parquet/nation.parquet"
    } ],
    storageengine : {
      type : "parquet",
      dfsName : "file:///"
    },
    ref : "_MAP",
    fragmentPointer : 0
  }, {
    pop : "project",
    @id : 2,
    exprs : [ {
      ref : "regionkey",
      expr : "_MAP.N_REGIONKEY"
    }, {
      ref : "nationkey",
      expr : "_MAP.N_NATIONKEY"
    } ],
    child : 1
  }, {
     @id: 3,
     child: 2,
     pop: "screen"
   }
  ]
}