Has_many through has_many relation issue in rails

Question

In my gaming project I have defined couple of models:

class Ticket
  belongs_to :user
  belongs_to :game

  has_and_belongs_to_many :payments, join_table: 'tickets_payments',
                                     association_foreign_key: 'transaction_id',
                                     class_name: 'Transaction'
end

class Transaction
  belongs_to :game

  has_and_belongs_to_many :tickets, join_table: 'tickets_payments'
end

class Game
  has_many :tickets
  has_many :paid_tickets, -> { joins(:payments) }, class_name: 'Ticket' # # inner join would return only tickets that have related payment; if the ticket has related payment, it indicates that it was bought/paid
  has_many :users, -> { distinct }, through: :paid_tickets
end

The basic idea is that user can see the tickets for the game (I generate 10 random tickets with game_id and user_id but without payment) and when he decides to buy it, I create a payment for the ticket which allows me to filter bought tickets by has_many relation defined on Game model.

Now, my Game class is not related directly to users, so in order to check i.e how many players bought tickets I can do this

Game.find(params[:id]).users.size

which as I believe should logically translate to something like this

Game.find(params[:id]).tickets.joins(:payments).map(&:user).uniq.size

However, the results will vary when there is more than one user who generated the tickets. In the first case I see 2 users (which is wrong, because only one of them actually bought the ticket) and in the second case I correctly receive 1. I was able to fix it some other way, but still it puzzles my why this happens.

From my research I discovered that somehow relation

has_many :users, -> { distinct }, through: :paid_tickets

doesn't see joins(:payments) defined in paid_tickets has_many relation. I can literally put anything instead of :payments (like joins(:asdasd)) and it will take all the tickets and still return 2.

Does anyone have a clue why this happens?

Answer 1

I suppose the issue is already fixed and is merged into master, but yet not in stable version (should be fixed in 6.0.3.4). You can consider running self-defined query in this scope to join things for now.