How to bind multiple query results in angularfire2 with firestore? - firebase

Question

I would like to use a collection to maintain relation between some documents as proposed here (but slightly modified approach). I have chosen collection approach because it seems more scalable that document properties over time.
My actual data scructure
users
user1
user2
companies
co1
co2
user_co
user1
companies (collection)
co1
co2
user2
companies (collection)
co1
But with that approach, I need to do multiple queries in order to get all available companies for a specific user as we cannot perform "IN" clause.
So I need retrieve data in 2 steps:
retrieve list of company user have access to in user_co/{user}/companies
retrieve actual companies from /companies/{id}
Why 2 steps? Because I don't want to give read access to all companies to all users and querying /companies would then trigger access error­.
So I got struggle with how to retrieve a single bindable list of documents retrieved from multiple calls?
I got 2 items displayed in my component but field values does not get displayed. I certainly do something wrong in the way I retrieve /company documents.
Any help would be greatly appreciated.
MyService.ts
interface Company {
Name: string;
Owner: any;
id?: any;
time?: any;
creationTime?: any;
}
interface MyCompany {
id?: any;
Name: string;
}
#Injectable()
export class CompanyService {
companiesCollection: AngularFirestoreCollection<Company>;
myCompaniesCollection: AngularFirestoreCollection<MyCompany>;
myCompanies;
constructor(private afs: AngularFirestore, private ats: AuthService) {
this.myCompaniesCollection = this.afs.collection('user_co').doc(this.ats.currentUserId).collection('companies');
this.myCompanies = this.myCompaniesCollection.snapshotChanges().map(actions => {
return actions.map(a => {
// What is the good way to retrieve /companies data from here?
return this.afs.firestore.collection("companies").doc(a.payload.doc.id).get().then(doc => {
return { id: doc.id, ...doc.data() }
}).catch(error => {
console.log("Error reading company document:", error);
});
// Original example that return data from /user_co
//return { id: a.payload.doc.id, ...a.payload.doc.data() }
})
});
}
getData() {
return this.myCompanies;
}
}
using angularfire2 5.0.0-rc.3 with firebase 4.5.2

Answer 1

I've finally changed the way I store data into Firestore.
As mentionned here and in many docs related to NoSQL, denormalization is the way to go to avoid "join like" and multiple queries.
Using denormalization one can group all data that is needed to process
a query in one place. This often means that for different query flows
the same data will be accessed in different combinations. Hence we
need to duplicate data, which increases total data volume.
That way, I can simply retrieve /users/{user}/companies and get all relevant info about companies user belongs to. And there is no need to be able to access all company info (settings, users, etc) for all users anyway.
New data structure
/users/{user}
user_name
/companies/{company}
company_name
/companies/{company}
name
/admins/{user}
/users/{user}
user_name
Security rules allowing admins to invite/add users to company
match /users/{usr}/companies/{co} {
// Only visible to the actual user
allow read: if request.auth.uid == usr;
// Current user can opt-out of company
allow delete: if request.auth.uid == usr ||
// Company admin can add or drop-out a user
exists(/databases/$(db)/documents/companies/$(co)/admins/$(request.auth.uid));
// Company admin can add or drop-out a user
allow create, update: if exists(/databases/$(db)/documents/companies/$(co)/admins/$(request.auth.uid));
}
match /companies/{co} {
// Company accessible for members and admins only
allow read: if
exists(/databases/$(db)/documents/companies/$(co)/members/$(request.auth.uid)) ||
exists(/databases/$(db)/documents/companies/$(co)/admins/$(request.auth.uid));
match /admins/{usr} {
// allow company creation if it does not exists
allow create: if exists(/databases/$(db)/documents/companies/$(co)) == false
// updates allowed for admins
allow update, delete: if exists(/databases/$(db)/documents/companies/$(co)/admins/$(request.auth.uid));
}
match /users/{usr} {
// writes allowed for admins
allow write: if exists(/databases/$(db)/documents/companies/$(co)/admins/$(request.auth.uid));
}
}
Counterpart
When updating /companies/{company}/[name], I also need to retrieve all users that belongs to that company through /companies/{company}/users and then update all docs in /users/{user}/companies/{company}. This can be made within a single transaction.