[Mongo] 按时间分组统计（时间格式化），mongo分组

[Mongo] 按时间分组统计（时间格式化），mongo分组

/* 0 */
{
  "_id" : ObjectId("541fcc51c6c36038bc6b81cd"),
  "url" : "http://wifi21.com/",
  "addtime" : ISODate("2014-08-19T00:15:02Z")
}

/* 1 */
{
  "_id" : ObjectId("541fcc51c6c36038bc6b81ce"),
  "url" : "http://meiwen.me/src/index.html",
  "addtime" : ISODate("2014-08-19T00:15:07Z")
}
...

统计代码：

db.msds_accessrecord.group({
 keyf : function(doc){
	var date = new Date(doc.addtime);
	var dateKey = ""+date.getFullYear()+"-"+(date.getMonth()+1)+"-"+date.getDate();
	return {'day':dateKey}; //33
}, 
 initial : {"count":0}, 
 reduce : function Reduce(doc, out) {
	if(doc.url){
		out.count +=1;
	}
}
});

统计结果：

[
        {
                "day" : "2014-8-19",
                "count" : 41
        },
        {
                "day" : "2014-8-22",
                "count" : 28
        },
        ...
]

参考： http://stackoverflow.com/questions/5168904/group-by-dates-in-mongodb