Cannot query nested document's _id (other fields work) - mongodb

Question

I want to find all documents where vendor._id has a certain value. Below is the code, I tried, but it returns nothing.
let name = sampleData.name, _id = sampleData._id
Product.find({"vendor._id":ObjectID(_id)}).then((products) => {
//returns empty array
})
With the same method I tried to query a different field and it works. But I want to query with _id because other fields could vary with time.
Product.find({"vendor.name":name}).then((products) => {
//returns all documents that satisfy the condition.
})
Below is a sample document which I want to find
{
"status" : "active",
"connectedFarms" : [
{
"_id" : "5c412c62bf8a6602f04ae0bf",
"status" : "inActive",
"margin" : 10,
"price" : 55
},
{
"_id" : "5c4567bcb3845b0536a4d92e",
"status" : "inActive",
"margin" : 20,
"price" : 60
},
{
"_id" : "5c4567c4b3845b0536a4d931",
"status" : "active",
"margin" : 7,
"price" : 53.5
}
],
"vendor" : {
"_id" : ObjectId("5c3fcc0c7657ee02ac24bc21"),
"name" : "manna"
}
}
And here is the schema for this document.
let ProductSchema = new mongoose.Schema({
vendor:{_id:String, name:String},
connectedFarms:[{_id:String, name:String, status:String, price:Number, margin:Number}],
status:{
type:String,
trim: true,
minlength:1
}
});

Answer 1

Let's take a different approach on this, and make vendor its own schema. Mongoose does not allow you to nest schemas, so you cannot make the vendor._id a true ObjectID.
Vendor Schema
const VendorSchema = new mongoose.Schema({
name: string
});
module.exports = mongoose.model('Vendor', VendorSchema);
Product Schema
const ProductSchema = new mongoose.Schema({
vendor: {
type: mongoose.Types.ObjectID,
ref: 'Vendor'
},
connectedFarms: [{
_id: String,
name: String,
status: String,
price: Number,
margin: Number
}],
status: {
type: String,
trim: true,
minlength: 1
}
});
module.exports = mongoose.model('Product', ProductSchema);
Now when you want to query a product based on the vendors _id, it's very simple! All you need to do is supply the _id of the vendor in the query. NOTE: There is no reason to convert the _id to an ObjectID in the query, as mongoose accepts strings and converts them later on.
Query
const vendorID = myVendor._id;
Product.find({ vendor: vendorID })
.then((products) => {
// Do something with the found products
});
That's it! Much simpler to do, and much cleaner in the database. The vendor field is now easier to reference. You also have the ability to get the full vendor object in a query if desired by populating in the query. The difference is, the population will return the vendor name and _id, rather than just the _id. To do this, run the following:
Product.find({ vendor: vendorID })
.populate('vendor')
.then((products) => {
// Do something with the populated found products
});