您可以先用“项目”来做这样的事情,但对我来说,这是一个有点反直觉,需要一个$项目的舞台：

Aggregation agg = newAggregation(

project("quantity")

.andExpression("dayOfMonth(date)").as("day")

.andExpression("month(date)").as("month")

.andExpression("year(date)").as("year")

.andExpression("price * quantity").as("totalAmount"),group(fields().and("day").and("month").and("year"))

.avg("quantity").as("averavgeQuantity")

.sum("totalAmount").as("totalAmount")

.count().as("count")

);

就像我所说的,反直觉,你应该能够宣布所有这些在$group阶段,但帮助者似乎不这样工作.序列化有点有趣(用数组包装日期操作符参数),但它似乎工作.但是,这是两个管道阶段,而不是一个.

这是什么问题？通过分阶段,“项目”部分强制处理流水线中的所有文档,以获得计算的字段,这意味着它在移动到组阶段之前通过所有的阶段.

通过以两种形式运行查询可以清楚地看到处理时间的差异.在单独的项目阶段,我的硬件执行时间要比在“组”操作期间计算所有字段的查询多三倍.

所以现在看来​​唯一正确的方法是通过自己建立管道对象：

ApplicationContext ctx =

new AnnotationConfigApplicationContext(SpringMongoConfig.class);

MongoOperations mongoOperation = (MongoOperations) ctx.getBean("mongoTemplate");

BasicDBList pipeline = new BasicDBList();

String[] multiplier = { "$price","$quantity" };

pipeline.add(

new BasicDBObject("$group",new BasicDBObject("_id",new BasicDBObject("month",new BasicDBObject("$month","$date"))

.append("day",new BasicDBObject("$dayOfMonth","$date"))

.append("year",new BasicDBObject("$year","$date"))

)

.append("totalPrice",new BasicDBObject(

"$sum",new BasicDBObject(

"$multiply",multiplier

)

))

.append("averageQuantity",new BasicDBObject("$avg","$quantity"))

.append("count",new BasicDBObject("$sum",1))

)

);

BasicDBObject aggregation = new BasicDBObject("aggregate","collection")

.append("pipeline",pipeline);

System.out.println(aggregation);

CommandResult commandResult = mongoOperation.executeCommand(aggregation);

或者如果所有这些似乎都简化了,那么你可以随时使用JSON源并解析.但当然,它必须是有效的JSON：

String json = "[" +

"{ \"$group\": { "+

"\"_id\": { " +

"\"month\": { \"$month\": \"$date\" }," +

"\"day\": { \"$dayOfMonth\":\"$date\" }," +

"\"year\": { \"$year\": \"$date\" } " +

"}," +

"\"totalPrice\": { \"$sum\": { \"$multiply\": [ \"$price\",\"$quantity\" ] } }," +

"\"averageQuantity\": { \"$avg\": \"$quantity\" }," +

"\"count\": { \"$sum\": 1 } " +

"}}" +

"]";

BasicDBList pipeline = (BasicDBList)com.mongodb.util.JSON.parse(json);