mongodb - 如何只从 Mongodb 聚合中返回一些字段($project),同时还使用 $match、$lookup 和 $filter
问题描述
我非常接近从这个查询中得到我想要的东西......但我只想要返回一些字段,现在它正在返回所有这些字段
注意:这是一个改进:我现在询问如何仅返回某些字段,而我的类似问题询问如何返回开始日期和结束日期之间的数据
此外,有人可以请使用带有我的数据集的MongoDB Playground提供答案,以便我可以尝试一下……我不太清楚如何“命名”数据集,以便它们在操场上工作!
注册架构
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const RegisterSchema = new Schema({
userId: {type: Schema.Types.ObjectId, required: true},
accessToken: {type:String, required: true, default: null},
})
module.exports = Register = mongoose.model( 'register', RegisterSchema)
这是一些寄存器数据
[
{
"_id": "5eac9e815fc57b07f5d0d29f",
"userId": "5ea108babb65b800172b11be",
"accessToken": "111"
},
{
"_id": "5ecaeba3c7b910d3276df839",
"userId": "5e6c2dddad72870c84f8476b",
"accessToken": "222"
}
]
下一个文档包含通过 accessToken 与 Register 模式相关的数据
通知
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const NotificationSchema = new Schema({
accessToken: {type:String, required: true},
summaryId: {type:Number, required: true},
dateCreated: {type: Date, default: Date.now},
// I don't want these returned in the final results
dontWantThis1: {type:Number, required: true},
dontWantThis2: {type:Number, required: true},
})
module.exports = Notification = mongoose.model( 'notification', NotificationSchema)
这是一些通知数据
[{
"_id": "5ebf0390c719e60004f42e74",
"accessToken": "111",
"summaryId": 1111,
"dontWantThis1": 61,
"dontWantThis2": 62,
"dateCreated": "2020-04-17T00:00:00.000+00:00" },
{
"_id": "6ebf0390c719e60004f42e76",
"accessToken": "222",
"summaryId": 2221,
"dontWantThis1": 71,
"dontWantThis2": 72,
"dateCreated": "2020-04-18T00:00:00.000+00:00" },
{
"_id": "6ebf0390c719e60004f42e78",
"accessToken": "111",
"summaryId": 1112,
"dontWantThis1": 611,
"dontWantThis2": 622,
"dateCreated": "2020-05-25T00:00:00.000+00:00" },
{
"_id": "6ebf0390c719e60004f42e80",
"accessToken": "222",
"summaryId": 2222,
"dontWantThis1": 711,
"dontWantThis2": 722,
"dateCreated": "2020-05-26T00:00:00.000+00:00" }
]
有效,返回两个日期之间的数据,但是
此代码返回所有内容,包括“dontWantThis1”和“dontWantThis2”
笔记
我不希望以“dontWantThis”开头的字段 - 但这只是为了显示我不想要的字段......我并不想排除以“dontWantThis”开头的字段.....它们可能是命名为 'foo' 或 'apple' 或 'dog' 他们只是这样命名以表明我不想要它们
// make sure the input dates are REALLY date objects
// I only want to see notifications for the month of May (in this example)
var dateStart = new Date('2020-05-01T00:00:00.000+00:00');
var dateEnd = new Date('2020-05-30T00:00:00.000+00:00');
var match = {$match: { userId: mongoose.Types.ObjectId(userId) } };
var lookup ={
$lookup:
{
from: "my_Notifications",
localField: "accessToken",
foreignField: "accessToken",
as: "notifications"
}
};
var dateCondition = { $and: [
{ $gte: [ "$$item.dateCreated", dateStart ] },
{ $lte: [ "$$item.dateCreated", dateEnd ] }
]}
var project = {
$project: {
notifications: {
$filter: {
input: "$notifications",
as: "item",
cond: dateCondition
} } }
};
var agg = [
match,
lookup,
project
];
Register.aggregate(agg)
.then( ..... )
试试 1
我以为我可以做这样的事情,但它仍然返回所有通知字段
var project = {
$project: {
"_id": 1,
"userId": 1,
"accessToken":1,
"count":{$size:"$notifications"},
"notifications._id":1,
"notifications.summaryId": 1,
"notifications.dateCreated":1,
notifications : {
$filter: {
input: "$notifications",
as: "item",
cond: dateCondition
},
}}
};
解决方案
我创建了另一个投影并将其添加到管道中:
var project2 = {
$project: {
"_id": 1,
"userId": 1,
"accessToken":1,
"count":{$size:"$notifications"},
"notifications._id":1,
"notifications.summaryId": 1,
"notifications.dateCreated":1,
"notifications.dateProcessed":1,
}
};
var agg = [
match,
lookup,
project,
project2,
];
谢谢!!
解决方案
https://stackoverflow.com/users/6635464/ngshravil-py就在现场。
我创建了另一个投影:
var project2 = {
$project: {
"_id": 1,
"userId": 1,
"accessToken":1,
"count":{$size:"$notifications"},
"notifications._id":1,
"notifications.summaryId": 1,
"notifications.dateCreated":1,
"notifications.dateProcessed":1,
}
};
然后将其添加到我的聚合管道中:
var agg = [
match,
lookup,
project,
project2,
];
工作!-- 谢谢 https://stackoverflow.com/users/6635464/ngshravil-py