Firebase Cloudfirestore update elements in a collections - node.js

Question

i'm using firebase functions with nodejs and cloudfirestore to build an API, now i have a problem, i have a collection an inside the collection an array of objects.
My goal is to update only a specific element without read the whole object and then push it again.
This is how my "order's collection" looks like:
"someRestaurantId":[{id:1,desc:"test",val:3000},{id:2,desc:"test",val:4000},{id:4,desc:"test",val:5000}]
My goal es only update id 2.
This is what i been trying:
Get the full list based on
const document = db.collection('orders').doc(req.params.restId);
Iterate and find the correct element, modify it and update it again.
await document.update(fullobject)
The problem is that i need something more easy to handle since there could be thousand of element inside that array.

Answer 1

Looking at described issue, I think you should use subcollection (sometimes called nested collection) for that. However from the description it is hard to tell what do you have now.
Firestore collection structure is always like this:
collection -> document -> fields and nestedCollections
than nestedCollection has the same structure, so you can nest whole structure how many times you want, but always collection contain only documents and each document contain only fields and collection.
In presented collection description array is directly in the collection or directly in document which both are impossible.
Anyway my idea is to structure it following way:
Collection orders containing docs of various restIDs
every docs (ex. "someRestaurantId") contain subcollection with name ex. "RestOrders"
in the subcollection will add documents with ids like (1,2,3 etc.)
every doc in subcollection will have fields desc, val
Collection Orders:
Document RestID_1:
Subcolection RestOrders:
Document 1: {val: 3000, desc: test}
Document 2: {val: 3000, desc: test}
...
Document RestID_2:
Subcolection RestOrders:
Document 1: {val: 3000, desc: test}
Document 2: {val: 3000, desc: test}
...
And now to update value of "RestID_1", order "id 2" you can use:
db.collection('Orders')
.doc('RestID_1')
.collection('RestOrders')
.doc('2')
.update( {val: 4000} )
In above solution you avoid reading and updating big array. You can update only one filed of one document in nested sub-collection.