mongodb的高级操作（聚合框架）

group by 查询 不要用java驱动带的group by ，要用2.2版本后的aggregate聚合框架来搞，经过试验速度快一倍

参考

官网：http://docs.mongodb.org/manual/reference/sql-aggregation-comparison/
实例：http://www.yeetrack.com/?p=649

观看例子前，请先看上面对的2个参考文档，特别是官网的

例子 

// 首先利$match筛选出where条件
BasicDBObject[] array = {
        new BasicDBObject("startTimeLong", new BasicDBObject("$gte",beginTime)),
        new BasicDBObject("startTimeLong", new BasicDBObject("$lt",endTime)) };

BasicDBObject cond = new BasicDBObject();
cond.put("$and", array);
DBObject match = new BasicDBObject("$match", cond);

// 利用$project拼装group需要的数据，包含optCode列、processTime列
DBObject fields = new BasicDBObject("optCode", 1); // 接口
fields.put("processTime", 1);// 耗时
fields.put("provinceCode", 1);// 省份
fields.put("channelSubCode", 1);// 渠道
fields.put("platFormCode", 1);// 平台

DBObject project = new BasicDBObject("$project", fields);

// 利用$group进行分组
DBObject _group = new BasicDBObject("provinceCode", "$provinceCode");
_group.put("channelSubCode", "$channelSubCode");
_group.put("platFormCode", "$platFormCode");
_group.put("optCode", "$optCode");

DBObject groupFields = new BasicDBObject("_id", _group);
//总数
        groupFields.put("count", new BasicDBObject("$sum", 1));
              //求和
groupFields.put("processTime_sum", new BasicDBObject("$sum","$processTime"));
              DBObject group = new BasicDBObject("$group", groupFields);
AggregationOutput output = MongodbUtil.getLogInfoCollection().aggregate(match, project, group);