我只想从每组字段中获取一个元素: 这是我的结果
[{
"_id":{"device_id":"9"},"x":["2019-11-17T18:03:33.000Z","2019-11-17T12:02:35.000Z"],"y":["93","3"]
},{
"_id":{"device_id":"8"},"x":["2019-11-16T12:05:33.000Z","2019-11-16T12:02:35.000Z"],"y":["33","3"]
}]
我只想获取最后插入的数据,意味着x中只有一个值,而y中只有一个值。 这是代码:
aggregate([
{ "$sort": { "timeStamp": -1 } },{
$group:
{
_id: { device_id: '$device_id' },x: {
$push: "$timeStamp"
},y: {
$push: "$value"
},device_name: {
$push: "$device_name"
},}
}
}]
我试图添加项目exp:
{
$project: {
time: "$x",value:"$y",integerValues:{
$map:{
input: "x",as: "integerValue",in: { $trunc: "$$integerValue" }
}
}
}
}
这是我期望得到的结果:
{
"_id":{"device_id":"8"},"x":["2019-11-16T12:05:33.000Z"],"y":["33"]
},{
"_id":{"device_id":"9"},"x":["2019-11-17T18:03:33.000Z"],"y":["93"]
}
我在没有任何解决方案的情况下搜索了如此多的问题