MongoDB create product summary collection - node.js

Question

Say I have a product collection like this:
{
"_id": "5a74784a8145fa1368905373",
"name": "This is my first product",
"description": "This is the description of my first product",
"category": "34/73/80",
"condition": "New",
"images": [
{
"length": 1000,
"width": 1000,
"src": "products/images/firstproduct_image1.jpg"
},
...
],
"attributes": [
{
"name": "Material",
"value": "Synthetic"
},
...
],
"variation": {
"attributes": [
{
"name": "Color",
"values": ["Black", "White"]
},
{
"name": "Size",
"values": ["S", "M", "L"]
}
]
}
}
and a variation collection like this:
{
"_id": "5a748766f5eef50e10bc98a8",
"name": "color:black,size:s",
"productID": "5a74784a8145fa1368905373",
"condition": "New",
"price": 1000,
"sale": null,
"image": [
{
"length": 1000,
"width": 1000,
"src": "products/images/firstvariation_image1.jpg"
}
],
"attributes": [
{
"name": "Color",
"value": "Black"
},
{
"name": "Size",
"value": "S"
}
]
}
I want to keep the documents separate and for the purpose of easy browsing, searching and faceted search implementation, I want to fetch all the data in a single query but I don't want to do join in my application code.
I know it's achievable using a third collection called summary that might look like this:
{
"_id": "5a74875fa1368905373",
"name": "This is my first product",
"category": "34/73/80",
"condition": "New",
"price": 1000,
"sale": null,
"description": "This is the description of my first product",
"images": [
{
"length": 1000,
"width": 1000,
"src": "products/images/firstproduct_image1.jpg"
},
...
],
"attributes": [
{
"name": "Material",
"value": "Synthetic"
},
...
],
"variations": [
{
"condition": "New",
"price": 1000,
"sale": null,
"image": [
{
"length": 1000,
"width": 1000,
"src": "products/images/firstvariation_image.jpg"
}
],
"attributes": [
"color=black",
"size=s"
]
},
...
]
}
problem is, I don't know how to keep the summary collection in sync with the product and variation collection. I know it can be done using mongo-connector but i'm not sure how to implement it.
please help me, I'm still a beginner programmer.

Answer 1

you don't actually need to maintain a summary collection, its redundant to store product and variation summary in another collection
instead of you can use an aggregate pipeline $lookup to outer join product and variation using productID
aggregate pipeline
db.products.aggregate(
[
{
$lookup : {
from : "variation",
localField : "_id",
foreignField : "productID",
as : "variations"
}
}
]
).pretty()