MongoDB - query ObjectId nested array

I have a collection named Product on MongoDB with some documents, here is an example:


_id: 'xxxxxx',
name: 'cellphone',
brands: [
'aaaaaa',
'bbbbbb'
]



The 'brands' key makes reference to another collection named Brand, example:

[

_id: 'aaaaaa',
name: 'Apple',
_deprecatedDate: null
,

_id: 'bbbbbb',
name: 'BlackBerry',
_deprecatedDate: '2016-07-13T02:27:17.724Z'

]


So, with a Product id, I want to get all it's non-deprecated brands.
The only way I found to do that is with the following code:

let _product = await Product.findOne( _id: 'xxxxxx' );
return Brand.find( _id: $in: _product.brands , _deprecatedDate: null );


Is there a way to do that with one single query?

1 Answer
1

You can use .aggregate() and $lookup to fetch the data from multiple collections. You can either specify custom pipeline (MongoDB 3.6):

.aggregate()

pipeline

Product.aggregate([

$lookup:
from: "Brand",
let: brands: "$brands" ,
pipeline: [

$match:
$expr:
$and: [
$in: [ "$_id", "$$brands" ] ,
$eq: [ "$_deprecatedDate", null ]
]



],
as: "brands"


])


or just use $lookup with $filter in next stage to filter out deprecated brands:

$lookup

Product.aggregate([

$lookup:
from: "Brand",
localField: "brands",
foreignField: "_id",
as: "brands"

,

$addFields:
brands:
$filter:
input: "$brands",
as: "brand",
cond:
$eq: [ "$$brand._deprecatedDate", null ]





])


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