Create view from 2 different collections in mongoDB - json

Question

I want to create a view from 2 different collections(info1, info2) in mongodb.
I need to have LoginId, FirstName,LastName,Email from info1 collection and GroupName,Type,MachName from info2 collection. Connecting field between info1 and info2 collections are "GroupName" and "Group" respectively
Below the collection content:
info1:
{
"GroupName" : "TEST Group1",
"LoginId" : "login1",
"FirstName" : "John",
"LastName" : "deo",
"Email" : "john.deo#xyz.com"
}
{
"GroupName" : "TEST Group2",
"LoginId" : "login1",
"FirstName" : "John",
"LastName" : "deo",
"Email" : "john.deo#xyz.com"
}
{
"GroupName" : "TEST Group2",
"LoginId" : "login2",
"FirstName" : "Mark",
"LastName" : "Clan",
"Email" : "mark.clan#xyz.com"
}
info2:
{
"Group" : "TEST Group1",
"Type" : "DEV",
"ActiveFlag" : "True",
"MachName" : "group1.xyz.net",
}
{
"Group" : "TEST Group2",
"Type" : "DEV",
"ActiveFlag" : "True",
"MachName" : "group2.xyz.net",
}
{
"Group" : "TEST Group1",
"Type" : "UAT",
"ActiveFlag" : "True",
"MachName" : "group1.xyz.net",
}
{
"Group" : "TEST Group2",
"Type" : "UAT",
"ActiveFlag" : "True",
"MachName" : "group2.xyz.net",
}
I want to have output as below from the view.
Expected output:
{
"GroupName" : ["TEST Group1", "TEST Group2"]
"LoginId" : "login1",
"FirstName" : "John",
"LastName" : "deo",
"Email" : "john.deo#xyz.com",
"Type" : "DEV",
"MachName" : ["group1.xyz.net","group2.xyz.net"]
},
{
"GroupName" : ["TEST Group1", "TEST Group2"],
"LoginId" : "login1",
"FirstName" : "John",
"LastName" : "deo",
"Email" : "john.deo#xyz.com",
"Type" : "UAT",
"MachName" : ["group1.xyz.net","group2.xyz.net"]
},
{
"GroupName" : ["TEST Group2"],
"LoginId" : "login2",
"FirstName" : "Mark",
"LastName" : "Clan",
"Email" : "mark.clan#xyz.com",
"Type" : "DEV",
"MachName" : ["group2.xyz.net"]
},
{
"GroupName" : ["TEST Group2"]
"LoginId" : "login2",
"FirstName" : "Mark",
"LastName" : "Clan",
"Email" : "mark.clan#xyz.com",
"Type" : "UAT",
"MachName" : ["group2.xyz.net"]
}
I have tried with below but not able to get the expected output. Can someone please help me to have view which should give the expected output from the 2 collections(info1,info2)?
Tried code(not working):
db.getCollection("info1").aggregate(
[
{
"$lookup" : {
"from" : "info2",
"localField" : "GroupName",
"foreignField" : "Group",
"as" : "g"
}
} ,
{ $match: { $and: [ {"g.ActiveFlag" : "True"} ] } },
{
"$project" : {
"LoginId" : "$LoginId",
"FirstName" : "$FirstName",
"LastName" : "$LastName",
"Email" : "$Email",
"machName" : "$g.MachName"
}
}
],
{
"allowDiskUse" : false
}
);

Answer 1

Demo - https://mongoplayground.net/p/SX3xH1v_2wQ
Use $group
$first
$push
Groups input documents by the specified _id expression and for each distinct grouping, outputs a document. The _id field of each output document contains the unique group by value. The output documents can also contain computed fields that hold the values of some accumulator expression.
db.info1.aggregate([
{
"$lookup": {
"from": "info2",
"localField": "GroupName",
"foreignField": "Group",
"as": "g"
}
},
{
$match: {
$and: [
{
"g.ActiveFlag": "True"
}
]
}
},
{
$group: {
_id: null, // you can goup by LoginId if you want
GroupName: { $push: "$GroupName" },
MachName: { $push: { $first: "$g.MachName" } },
LoginId: { $first: "$LoginId" },
FirstName: { $first: "$FirstName" },
Email: { $first: "$Email" },
Type: { $first: { $first: "$g.Type" } },
}
}
])
Update
Updated Demo - https://mongoplayground.net/p/0AgT3FJIB6P
Use $unwind on g after lookup pipeline
{ $unwind: "$g" }
Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element.
Demo - https://mongoplayground.net/p/IGzTzEbgfl0
$group: {
_id: {
Type: "$g.Type",
LoginId: "$LoginId"
}
// ....
}