Problem using aggregation in mongodb retrieving data from two collections - mongodb

Question

i am strugling with a query that i don't know how to perform... I have two collections,
Tarifas Collection
tarifaConfig = new Schema({
producto: { type: String },
titulo: { type: String },
bloqueo: { type: Boolean },
margen: { type: Number },
precioVenta: { type: Number },
precioVentaIva: { type: Number },
})
const tarifaSchema = new Schema({
codigo: { type: String },
titulo: { type: String },
margen: { type: Number },
estado: { type: Boolean },
bloqueo: { type: Boolean },
configs: [tarifaConfig]
})
Producto Collection
const productosSchema = new Schema({
ref: { type: String },
nombre: { type: String },
precioCompra: { type: Number },
precioCompraIva: { type: Number },
precioVenta: { type: Number },
precioVentaIva: { type: Number },
iva: { type: Number },
})
Now i am using an Aggregation method to retrieve both collection in a response
productosModel.aggregate([
{
$match: { _id: ObjectId(req.params.id) }
},
{
$lookup: {
from: "tarifas",
as: "tarifas",
pipeline: []
}
}
]).then((producto) => {
res.json(producto);
})
This is working and gives me both collections in the response... but..
In tarifa's collection i have a propertie called 'configs' that is an array with lot of sub collections... this sub collections are a config of each product that i have,
So what i need to do is, retrieve all tarifas that has a configs for the product, and if the configs does not contain retrieve the tarifa with a empty array.
Expected result
{
ref: 'rbe34',
nombre: 'bike',
precioCompra: 10,
precioCompraIva: 12.1,
precioVenta: "",
precioVentaIva: "",
iva: 21,
tarifas:[
{
codigo: 'NOR',
titulo: 'Normal tarifa',
margen: 33,
estado: true,
bloqueo: true,
configs: [], ///HERE I NEED A EMPTY ARRAY IF THERE IS NOT ANY CONFIG THAT MATCH WITH THE PRODUCT ID,
}
]
}
i tried to add $match in my aggregation pipeline.
productosModel.aggregate([
{
$match: { _id: ObjectId(req.params.id) }
},
{
$lookup: {
from: "tarifas",
as: "tarifas",
pipeline: [
{ $match: { 'configs.producto': req.params.id } }
]
}
}
])
But if there is not any config that match the product it doesn't retrieve the rest of Tarifa's collection

Answer 1

It seems you are trying to $filter the array after you retrieve it.
This pipeline will return only the configs for which the producto field from the config matches the ref field from the product.
[
{
$match: { _id: ObjectId(req.params.id) }
},
{
$lookup: {
from: "tarifas",
as: "tarifas",
pipeline: [
{
$addFields: {
"tarifas.configs":{ $filter:{
input: "$tarifas.configs",
cond: {$eq:["$$this.producto","$ref"]}
} }
}
}
]
}
},
]
Change the fields in the $eq array to the ones you need to match.