How to structure sub node of collections in Firestore? - firebase

Question

I'm trying to migrate the following structure from real time database to Firestore :
• Resources
o SENT
 resId1
• name : xxxx
• url : xxx
 resI2
• name ……
o ACCEPT
 resId3
 etc……
o REFUSED
 restIdn
 etc….
So under root Node" Resources" I have some sub nodes (SENT, ACCEPT, REFUSED, ...) that contain List of resources items.
With Firestore it seems I can't have subCollection directly under collection (When I try to reproduce this structure with Firestore in the admin console I need to create an intermediate document like:
Collection --> document --> SubCollection --> documents
Witch lead to that structure:
Resources --> SENT --> SENT --> resId1 {name: xxx, url: yyyy}
So the sub node "SENT" is duplicated twice (one for the document and one for the sub collection).
This is not an improvement or a simplification at all, if I compare with firebase real time database.
Do I miss something? What is the best way for such kind of database structure?

Answer 1

(Edited 10/13/2017 # 11am)
It seems that there are two structures that will work for you.
Option 1: Three Root Collections
Create three collections at the root of your Firestore database
resources-sent
resources-accept
resources-refused
Each one contains documents.
Option 2: One Root Collection
Firestore allows for compound queries, so you could just make one collection at the root called resources and add a type parameter to each document where type is one of [sent, accept, refused].
Then you can do queries like this:
// Get all sent resources
db.collection("resources").where("type", "==", "sent").get()
Because of Firestore's built in indexes this query will always be fast!'
Option 3: Subcollections.
Create a root collection called resources containing only three docs:
sent
accept
refused
For each of these docs create a resources subcollection.
So to get all sent resources:
// Get all sent resources
db.collection("resources").doc("sent").collection("resources").get()