是否有一种方法可以计算具有特定截止日期的猫鼬的不同值

Question

例如，我有以下两个文档

[
{
"_id": "5fc534505144dd0030c44f8e",
"createdAt": "2020-12-14T15:11:21.327Z"
"user_id": "2",
},
{
"_id": "5fc534505144dd0030c44f8e",
"createdAt": "2020-12-14T14:10:40.427Z",
"user_id": "1"
},
{
"_id": "5fc534595144dd0030c44f95",
"createdAt": "2020-12-13T14:10:58.027Z",
"user_id": "1"
}
]

结果应为

[
{
"date": "2020-12-13",
"count":1
},
{
"date": "2020-12-14",
"count":2
}
]

中计数是在截止日期

之前通过user_ids的不同文档的数量。

Answer 1

给定数据

data=[
{
"createdAt": "2020-12-14T15:11:21.327Z",
"user_id": "2",
},
{
"createdAt": "2020-12-14T14:10:40.427Z",
"user_id": "1"
},
{
"createdAt": "2020-12-13T14:10:58.027Z",
"user_id": "1"
},{
"createdAt": new Date("2020-12-14T14:10:58.027Z"),
}
]
> db.dummy.insert(data)

您可以使用aggregate:使用$group与_id是日期的日子与$sum)

> db.dummy.aggregate({$group:{_id:{$substr:['$createdAt', 0, 10]}, count:{$sum:1}}})
{ "_id" : "2020-12-14", "count" : 3 }
{ "_id" : "2020-12-13", "count" : 1 }

---

edit: mongoose wise same may hold

const mongoose = require('mongoose')
mongoose.connect('mongodb://localhost:27017/dummy')
const UDate = mongoose.model('X', { createdAt:String, user_id: String }, 'dummy')
;(async()=>{
mongoose.set('debug', true)
const group = {$group:{_id:{$substr:['$createdAt', 0, 10]}, count:{$sum:1}}}
const v = await UDate.aggregate([group])
console.log('s : ', JSON.stringify(v))
mongoose.disconnect()
})()

edit2:要处理用户id的唯一性，因此每个日期不会计数两次，您可以使用$addToSet代替sum，然后使用$size

的投影

const group = {$group:{_id:{$substr:['$createdAt', 0, 10]}, userIds:{$addToSet:'$user_id'}}}
const count = {$project:{date:'$_id', count: {$size: '$userIds'}} }
const v = await Stock.aggregate([group, count])

最后，如果你总是感觉更多，你可以"重命名"。_id字段作为投影期间的日期

{$project:{date:'$_id', _id:0, count: {$size: '$userIds'}} }

Answer 2

• $gorup通过createdAt日期获取$substr的子字符串，并在$addToset的基础上生成唯一的用户id数组
• 使用$size获取count数组中的总元素

db.collection.aggregate([
{
$group: {
_id: { $substr: ["$createdAt", 0, 10] },
count: { $addToSet: "$user_id" }
}
},
{ $addFields: { count: { $size: "$count" } } }
])

游乐场