$aggregation and $look up in the same collection- mongodb not get child - node.js

Question

I have an product option schema where I have chield material and add-on type
Product_options
const productOptionsSchema = new mongoose.Schema({
category: [{
value: { type: String },
display: { type: Number },
display_order: { type: String },
categoryImage: { type: String },
parent_id: { type: mongoose.Schema.Types.ObjectId },
parent_name: { type: String }
}],
material: [{
value: { type: String },
display: { type: Number },
display_order: { type: String },
price: { type: String }
}],
addon_type: [{
// addon_id: {
type: mongoose.Schema.Types.ObjectId,
ref: 'AddOnDetails'
// }
}],
design: [{
// design_id: {
type: mongoose.Schema.Types.ObjectId,
ref: 'DesignDetails'
// }
}]
}, {
timestamps: true
})
const Product_options = mongoose.model('Product_options', productOptionsSchema)
i want to add one more key 'isChildExist' if have any chield of category have parent_id == parent_id . my node js code is
const cat = await Product_options.aggregate( [
{
$unwind: {
path: "$category",
preserveNullAndEmptyArrays: true
}
},
{
$lookup: {
from: 'Product_options.category',
localField: '_id',
foreignField: 'parent_id',
as: 'category.isChildExist'
}
},
{
"$project": {
"_id": 0,
"category": 1,
}
}
] );
res.json({
msg: 'Success!',
cat
})
my current response is whenre isChildExist is blank :
{
"msg": "Success!",
"cat": [
{
"category": {
"value": "Rudraksha",
"display": 1,
"display_order": "",
"categoryImage": "",
"parent_id": null,
"parent_name": null,
"_id": "63aeac69f969cf78856b7db9",
"isChildExist": []
}
},
{
"category": {
"value": "Bead Bracelet",
"display": 1,
"display_order": "",
"categoryImage": "",
"parent_id": null,
"parent_name": null,
"_id": "63aeae05f969cf78856b80b2",
"isChildExist": []
}
},
{
"category": {
"value": "Gemstones",
"display": 1,
"display_order": "1",
"categoryImage": "",
"parent_id": null,
"parent_name": null,
"_id": "63aeb968f969cf78856b8cd9",
"isChildExist": []
}
},
{
"category": {
"value": "Natural Yellow Sapphire - Pukhraj ",
"display": 1,
"display_order": "1",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aec39bf969cf78856bb9c3",
"isChildExist": []
}
},
{
"category": {
"value": "Natural Blue Sapphire - Neelam",
"display": 1,
"display_order": "1",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aebe42f969cf78856b9fae",
"isChildExist": []
}
},
{
"category": {
"value": "Natural Ruby - Manik ",
"display": 1,
"display_order": "",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aebe54f969cf78856b9fd9",
"isChildExist": []
}
},
{
"category": {
"value": "Natural Hessonite - Gomed",
"display": 1,
"display_order": "",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aebe83f969cf78856ba076",
"isChildExist": []
}
},
{
"category": {
"value": "Natural Coral - Moonga ",
"display": 1,
"display_order": "",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aebe9ff969cf78856ba0a8",
"isChildExist": []
}
},
{
"category": {
"value": "Natural Emerald - Panna ",
"display": 1,
"display_order": "",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aebeb5f969cf78856ba0de",
"isChildExist": []
}
}
]
}
i expect isChildExist have data in gemstone but current is blank array
{
"category": {
"value": "Gemstones",
"display": 1,
"display_order": "1",
"categoryImage": "",
"parent_id": null,
"parent_name": null,
"_id": "63aeb968f969cf78856b8cd9",
"isChildExist": [
{
"value": "Natural Yellow Sapphire - Pukhraj ",
"display": 1,
"display_order": "1",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aec39bf969cf78856bb9c3",
"child": []
},{
"value": "Natural Blue Sapphire - Neelam",
"display": 1,
"display_order": "1",
"categoryImage": "",
"parent_id": "63aeb968f969cf78856b8cd9",
"parent_name": "Gemstones",
"_id": "63aebe42f969cf78856b9fae",
"child": []
}
]
}
},

Answer 1

Problem is in $lookup
Try this code:
const cat = await Product_options.aggregate([{
$unwind: {
path: "$category",
preserveNullAndEmptyArrays: true
}
},
{
$lookup: {
from: 'Product_options',
let: {
category_id: "$category._id"
},
pipeline: [{
$match: {
$expr: {
$and: [{
$eq: ["$category.parent_id", "$$category_id"]
}, ]
}
}
},
{
$project: {
_id: 0,
category: 1,
}
}
],
as: "category.isChildExist"
}
},
{
$project: {
_id: 0,
category: 1
}
}
]);