MongoDB - MapReduce - Max e Min nel periodo

Utilizzo la piccola app del Meteo per fare qualche esperimento con le Map/Reduce
Devo ottenere il valore massimo e minino dei valori giornalieri, mensili e annuali da una collection contentente i logger raccolti ogni 5 minuti.

la collection sorgente (Meteolog):

{ "_id" : ObjectId("50d5a8a01e05acfe08c086fb"), "className" : "it.marcoberri.mbmeteo.model.Meteolog" , "n" : 1643, "time" : ISODate("2012-12-09T00:33:00Z"), "interval" : 5, "indoorHumidity" : 65, "indo orTemperature" : 19.5, "outdoorHumidity" : 72, "outdoorTemperature" : -0.6, "absolutePressure" : 997 .2, "wind" : 0, "gust" : 0.3, "direction" : "SE", "relativePressure" : 1025, "dewpoint" : -5, "windc hill" : -0.6, "hourRainfall" : 0, "dayRainfall" : 6.9, "weekRainfall" : 12.3, "monthRainfall" : 12.3 , "totalRainfall" : 12.3, "windLevel" : 0, "gustLevel" : 1 }

{ "_id" : ObjectId("50d5a8a01e05acfe08c086fc"), "className" : "it.marcoberri.mbmeteo.model.Meteolog" , "n" : 1644, "time" : ISODate("2012-12-09T00:38:00Z"), "interval" : 5, "indoorHumidity" : 65, "indo orTemperature" : 19.5, "outdoorHumidity" : 71, "outdoorTemperature" : -0.8, "absolutePressure" : 997 .3, "wind" : 0.3, "gust" : 0.7, "direction" : "S", "relativePressure" : 1025.1, "dewpoint" : -5.4, " windchill" : -0.8, "hourRainfall" : 0, "dayRainfall" : 6.9, "weekRainfall" : 12.3, "monthRainfall" : 12.3, "totalRainfall" : 12.3, "windLevel" : 1, "gustLevel" : 1 }
etc.


la funzionalità di map sul singolo giorno (variabile time_short)

map = function(){
    var fields =['outdoorTemperature','outdoorHumidity','absolutePressure','relativePressure','wind','gust','dewpoint','windchill',
'hourRainfall','dayRainfall','weekRainfall','monthRainfall','totalRainfall','windLevel','gustLevel'];

 var objs = {};

 for( var f=0; f<fields.length;f++) {
  var k = fields[f];
  objs[k] = { "min" : this[k], "max" : this[k]};
 }

 var time_short = this.time.getFullYear() + "-" + this.time.getMonth() + "-" + this.time.getDate();
 emit(time_short,objs)
}


La funzionalità di reduce:

reduce = function(key, values){
   var fields =['outdoorTemperature','outdoorHumidity','absolutePressure','relativePressure','wind','gust','dewpoint','windchill',
'hourRainfall','dayRainfall','weekRainfall','monthRainfall','totalRainfall','windLevel','gustLevel'];
   var res = values[0];
    for ( var i=1; i<values.length; i++ ) {
 for( var f=0; f<fields.length;f++) {
  var k = fields[f];
  var v = values[i][k];
         if ( v.min < res[k].min  )
            res[k].min = v.min;
         if ( v.max  > res[k].max  )
                   res[k].max = v.max;
 }
    }
    return res;
}

Usiamo le funzionalità:

db.Meteolog.mapReduce(map,reduce,{out:{merge:"reduceMaxMinDay"}});
db.reduceMaxMinDay.find();

result:

{ "_id" : "2012-11-23", "value" : { "outdoorTemperature" : { "min" : -2.3, "max" : 5.6 }, "outdoorHu midity" : { "min" : 79, "max" : 90 }, "absolutePressure" : { "min" : 996.8, "max" : 999 }, "relative Pressure" : { "min" : 1024.6, "max" : 1026.8 }, "wind" : { "min" : 0, "max" : 0.7 }, "gust" : { "min " : 0, "max" : 1 }, "dewpoint" : { "min" : -4.7, "max" : 2.4 }, "windchill" : { "min" : -2.3, "max" : 5.6 }, "hourRainfall" : { "min" : 0, "max" : 0 }, "dayRainfall" : { "min" : 0, "max" : 0 }, "weekR ainfall" : { "min" : 0, "max" : 0 }, "monthRainfall" : { "min" : 4.2, "max" : 4.2 }, "totalRainfall" : { "min" : 4.2, "max" : 4.2 }, "windLevel" : { "min" : 0, "max" : 1 }, "gustLevel" : { "min" : 0, "max" : 1 } } }

{ "_id" : "2012-11-9", "value" : { "outdoorTemperature" : { "min" : -2.3, "max" : 13.4 }, "outdoorHu midity" : { "min" : 26, "max" : 75 }, "absolutePressure" : { "min" : 992.9, "max" : 999.4 }, "relati vePressure" : { "min" : 1020.7, "max" : 1027.2 }, "wind" : { "min" : 0, "max" : 1 }, "gust" : { "min " : 0, "max" : 1.7 }, "dewpoint" : { "min" : -7.3, "max" : 0.3 }, "windchill" : { "min" : -2.3, "max " : 13.4 }, "hourRainfall" : { "min" : 0, "max" : 8.1 }, "dayRainfall" : { "min" : 0, "max" : 12.3 } , "weekRainfall" : { "min" : 0, "max" : 20.4 }, "monthRainfall" : { "min" : 0, "max" : 20.4 }, "tota lRainfall" : { "min" : 0, "max" : 20.4 }, "windLevel" : { "min" : 0, "max" : 1 }, "gustLevel" : { "m in" : 0, "max" : 2 } } } etc.

per modificare il periodo di calcolo basta modficare la variabile che permette il raggruppamento delle info:
es: mesile --> var time_short = this.time.getFullYear() + "-" + this.time.getMonth();
es: annulale -->  var time_short = this.time.getFullYear();