How to filter and display max values of each collection with flutter firestore

Question

I search a solution to extract all max value from all collections

I have a firestore structure like this

Collection      document          data


2020-08-01      user1       votes:1, data_user1
                user4       votes:4, data_user4     // =>win
                user8       votes:2, data_user8

2020-08-02      user11      votes:3, data_user11    // =>win
                user12      votes:2, data_user12
                user17      votes:1, data_user17

2020-08-03      user21      votes:3, data_user21    // =>win
                user23      votes:2, data_user23

So I try to filter and get in a list all wins data users

My_win_list:[
user4   :   data_user4
user11  :   data_user11
user21  :   data_user21
]

Answer 1

You can use ordering:

FirebaseFirestore.instance
  .collection('2020-08-01')
  .orderBy('votes', descending: true)
  .limit(1)
  .get()
  .then(...);

You can easily loops through the required collections as they seem to be dates. You can use Future.wait to run all promises simultaneously.