在下面的查询中,我正在对一个字段进行添加(该字段以 ISO 日期作为值),然后从该字段中提取小时,然后按小时分组
db.campaigns.aggregate([
{$group : { _id: {$hour:{$add:['$time', 19800000]}}}}
])
Sample record of the collection
db.campaigns.findOne()
{
"_id" : ObjectId("53c7afdab92be74745af9068"),
"time" : ISODate("2013-03-08T12:25:24.973Z"),
"type" : "annoying",
"PINGS" : 143
}
上面的在 Mongo shell 中运行良好,
我正在尝试用 Java 编写此查询
这是我的部分Java代码
DBObject group2Fields = new BasicDBObject();
group2Fields.put("hour", new BasicDBObject("$hour", new BasicDBObject("$add",new BasicDBObject("time",19800000))));
DBObject group2 = new BasicDBObject("_id", group2Fields);
DBObject secondGroup = new BasicDBObject("$group", group2);
我收到“errmsg”:“异常:$表达式内部不允许包含字段”
最佳答案
试试这个:
DBObject group2Fields = new BasicDBObject();
BasicDBList addObjects = new BasicDBList();
addObjects.add("$time");
addObjects.add(19800000);
group2Fields.put("$hour", new BasicDBObject("$add", addObjects));
DBObject group2 = new BasicDBObject("_id", group2Fields);
DBObject secondGroup = new BasicDBObject("$group", group2);
关于java - 如何在 MongoDB Java 驱动程序中编写带有添加操作的 group by,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25140739/