问题
I am VERY close to getting what I want out of this query... but I only want SOME of the fields returned and right now it is returning all of them
NOTE: This is a refinement : I am now asking how to return only certain fields, while my similar question asks how to return the data between a start and end date
In addition, can somebody please please provide an answer using the MongoDB Playground with MY data sets so I can try it out... I can't quite figure out how to "name" the data sets so they work in the playground !
Register Schema
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)
Here is some register data
[
{
"_id": "5eac9e815fc57b07f5d0d29f",
"userId": "5ea108babb65b800172b11be",
"accessToken": "111"
},
{
"_id": "5ecaeba3c7b910d3276df839",
"userId": "5e6c2dddad72870c84f8476b",
"accessToken": "222"
}
]
The next document contains data that is related to the Register schema via the accessToken
Notifications
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)
Here is some notification data
[{
"_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" }
]
Works, returns data between the two dates, but
This code returns everything, including the 'dontWantThis1' and 'dontWantThis2'
NOTE
I do not want the fields prefaced with 'dontWantThis' - but that is only to show which ones I don't want... I don't literally want to exclude fields prefaced with 'dontWantThis' ..... they could be named 'foo' or 'apple' or 'dog' they are just named that way to indicate that I don't want them
// 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( ..... )
Try 1
I thought I could do something like this, but it still returns ALL of the notification fields
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
},
}}
};
SOLUTION
I created another projection and added that to the pipeline:
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,
];
Thanks!!
回答1:
https://stackoverflow.com/users/6635464/ngshravil-py was spot on.
I created another projection:
var project2 = {
$project: {
"_id": 1,
"userId": 1,
"accessToken":1,
"count":{$size:"$notifications"},
"notifications._id":1,
"notifications.summaryId": 1,
"notifications.dateCreated":1,
"notifications.dateProcessed":1,
}
};
Then added it to my aggregation pipeline:
var agg = [
match,
lookup,
project,
project2,
];
Worked ! -- thank you https://stackoverflow.com/users/6635464/ngshravil-py
回答2:
You need to convert notifications.dateCreated to ISODate, as your date is in string, by using $dateFromString and $map operator. i suggest you to do this, because I don't think that you can do date comparison with string formats. Also, make sure that dateStart and dateEnd should also be in ISODate format.
And you need two $project operator in order to achieve this. Also, I don't see any field with userAccessToken, I assume, it's accessToken. Check the below query.
db.Register.aggregate([
{
$lookup: {
from: "my_Notifications",
localField: "accessToken",
foreignField: "accessToken",
as: "notifications"
}
},
{
$project: {
"_id": 1,
"userId": 1,
"accessToken": 1,
notifications: {
$map: {
input: "$notifications",
as: "n",
in: {
"_id": "$$n._id",
"summaryId": "$$n.summaryId",
"dateCreated": {
$dateFromString: {
dateString: "$$n.dateCreated"
}
}
}
}
}
}
},
{
$project: {
"userId": 1,
"accessToken": 1,
"notifications": {
$filter: {
input: "$notifications",
as: "item",
cond: {
$and: [
{
$gte: [
"$$item.dateCreated",
ISODate("2020-05-24T00:00:00Z")
]
},
{
$lte: [
"$$item.dateCreated",
ISODate("2020-05-26T00:00:00Z")
]
}
]
}
}
}
}
},
{
$set: {
"count": {
$size: "$notifications"
}
}
}
])
MongoPlayGroundLink
来源：https://stackoverflow.com/questions/62066169/how-do-i-only-return-some-fields-project-from-mongodb-aggregation-while-also