Mongo merge results - mongodb

Question

Hello guys I have 3 collections that have dbref, where I wanted to mount a result similar to the one shown below but I couldn't get to something satifatorio using any aggregate can you indicate a better way?
Coolections:
data1 - Main data_reference1
referenced in data1 data_reference2
referenced in data_reference2
/* EXAMPLE RECORD data1 */
{
"_id" : ObjectId("604fafd443487df824aeca61"),
"name" : "doc1",
"reference_data1_list" : [
{
"data_reference" : ObjectId("604fb00643487df824aeca91"),
"user_add" : "USER01"
},
{
"data_reference" : ObjectId("604fb00d43487df824aeca9b"),
"user_add" : "USER01"
},
{
"data_reference" : ObjectId("604fb01743487df824aecaa7"),
"user_add" : "USER02"
}
]
}
/* EXAMPLE RECORDS data_reference1 */
/* 1 */
{
"_id" : ObjectId("604fb00643487df824aeca91"),
"reference_desc" : "Test Referenced Field 01",
"reference_data2" : ObjectId("604fb24743487df824aecd14")
}
/* 2 */
{
"_id" : ObjectId("604fb00d43487df824aeca9b"),
"reference_desc" : "Test Referenced Field 02",
"reference_data2" : ObjectId("604fb24743487df824aecd14")
}
/* 3 */
{
"_id" : ObjectId("604fb01743487df824aecaa7"),
"reference_desc" : "Test Referenced Field 03",
"reference_data2" : ObjectId("604fb25743487df824aecd27")
}
/* EXAMPLE RECORDS data_reference2 */
/* 1 */
{
"_id" : ObjectId("604fb24743487df824aecd14"),
"name" : "Student"
}
/* 2 */
{
"_id" : ObjectId("604fb25743487df824aecd27"),
"name" : "Theacher"
}
Desired result:
{
"_id": ObjectId("604fafd443487df824aeca61"),
"name": "doc1",
"reference_data1_list": [
{
"_id": ObjectId("604fb00643487df824aeca91"),
"reference_desc": "Test Referenced Field 01",
"reference_data2": {
"_id": ObjectId("604fb24743487df824aecd14"),
"name": "Student"
}
},
{
"_id": ObjectId("604fb00d43487df824aeca9b"),
"reference_desc": "Test Referenced Field 02",
"reference_data2": {
"_id": ObjectId("604fb24743487df824aecd14"),
"name": "Student"
}
},
{
"_id": "604fb01743487df824aecaa7",
"reference_desc": "Test Referenced Field 03",
"reference_data2": {
"_id": ObjectId("604fb25743487df824aecd27"),
"name": "Theacher"
}
}
]
}
I don't have much skill with the mongo and I didn't find any similar example to be able to use in the example.

Answer 1

Try this query:
db.data1.aggregate([
{ $unwind: "$reference_data1_list" },
{
$lookup: {
from: "data_reference1",
let: {
data_ref: "$reference_data1_list.data_reference",
user_add: "$reference_data1_list.user_add"
},
pipeline: [
{
$match: {
$expr: { $eq: ["$_id", "$$data_ref"] }
}
},
{
$addFields: { user_add: "$$user_add" }
}
],
as: "reference_data1_list"
}
},
{ $unwind: "$reference_data1_list" },
{
$lookup: {
from: "data_reference2",
localField: "reference_data1_list.reference_data2",
foreignField: "_id",
as: "reference_data1_list.reference_data2"
}
},
{ $unwind: "$reference_data1_list.reference_data2" },
{
$group: {
_id: "$_id",
name: { $first: "$name" },
reference_data1_list: { $push: "$reference_data1_list" }
}
}
]);
Output
{
"_id" : ObjectId("604fafd443487df824aeca61"),
"name" : "doc1",
"reference_data1_list" : [
{
"_id" : ObjectId("604fb00643487df824aeca91"),
"reference_desc" : "Test Referenced Field 01",
"reference_data2" : {
"_id" : ObjectId("604fb24743487df824aecd14"),
"name" : "Student"
},
"user_add" : "USER01"
},
{
"_id" : ObjectId("604fb00d43487df824aeca9b"),
"reference_desc" : "Test Referenced Field 02",
"reference_data2" : {
"_id" : ObjectId("604fb24743487df824aecd14"),
"name" : "Student"
},
"user_add" : "USER01"
},
{
"_id" : ObjectId("604fb01743487df824aecaa7"),
"reference_desc" : "Test Referenced Field 03",
"reference_data2" : {
"_id" : ObjectId("604fb25743487df824aecd27"),
"name" : "Theacher"
},
"user_add" : "USER02"
}
]
}