db.runCommand({
    mapreduce : "watteco_wip_task",
    query : {date : {$gt : ISODate("2012-02-08T00:00:00"), $lt:ISODate("2012-02-08T23:59:59")}},
    map : function() {
        emit(
            {host: this.host},
            {n : 1}
        );
    },
    reduce: function(keys, vals) {
        var ret = {n : 0};
        for (var i=0; i<vals.length; i++) {
            ret.n += vals[i].n;
        }
        return ret;
    },
    out: {inline : 1}
});