如何通过关系通过has_many缩短三联Join ActiveRecord查询？

Question

I'm trying to clean up a very long ActiveRecord query. The one I have is working, though it hurts to look at it. Here's what is happening.

1) User has_many Simulations through UserSimulations (and vice versa).

2) User has_many Groups through UserGroups (and vice versa).

3) Group has_many Simulations through SimulationGroups (and vice versa).

What ends up happening here is that a user can be associated to a Simulation in two ways, either directly through the has_many to has_many relationship, or indirectly through a Group that the user belongs to.

I've been able to gather all the Simulations a User has access to in a single query, and it looks like this. I have access to the current_user object where the query needs to be called.

# Define Queries
user_sim_join = "LEFT JOIN user_simulations ON user_simulations.simulation_id = simulations.id"
user_grp_join = "LEFT JOIN user_groups ON user_groups.group_id = groups.id"
where_clause  = ["user_groups.user_id = :user_id OR user_simulations.user_id = :user_id", { user_id: user.id }]

# Run Query
Simulation.joins(user_sim_join, :groups, user_grp_join).where(where_clause).group('simulations.id') 

#=> Simulation Load (1.1ms)  SELECT "simulations".* FROM "simulations" 
         INNER JOIN "simulation_groups" ON "simulation_groups"."simulation_id" = "simulations"."id" 
         INNER JOIN "groups" ON "groups"."id" = "simulation_groups"."group_id" 
         LEFT JOIN user_simulations ON user_simulations.simulation_id = simulations.id 
         LEFT JOIN user_groups ON user_groups.group_id = groups.id 
         WHERE (user_groups.user_id = 2 OR user_simulations.user_id = 2) 
         GROUP BY simulations.id

I'm happy that it's working but would like to clean it up as to be more concise (not 4 lines of code to build a single query).

UPDATE

Here are the models involved.

Simulation.rb

class Simulation < ApplicationRecord
  # Associations
  belongs_to :company

  has_many :simulation_groups
  has_many :user_simulations
  has_many :objection_responses

  has_many :groups, through: :simulation_groups
  has_many :users, through: :user_simulations

  has_many :reports, as: :reportable
  has_many :objections, as: :objectionable

  # Validations
end

Group.rb

class Group < ApplicationRecord
  belongs_to :company
  has_many :simulation_groups
  has_many :simulations, through: :simulation_groups
  has_many :user_groups
  has_many :users, through: :user_groups
  has_many :minigame_groups
  has_many :minigames, through: :minigame_groups
  has_many :reports, through: :users

  # Validations
end

User.rb

class User < ApplicationRecord
  # Associations
  belongs_to :company

  has_one  :avatar
  has_many :reports
  has_many :events
  has_many :training_sessions
  has_many :user_groups
  has_many :groups, through: :user_groups
  has_many :objection_responses
  has_many :user_simulations
  has_many :simulations, through: :user_simulations
  has_many :minigame_users
  has_many :minigames, through: :minigame_users

  # Validations
end

Answer 1

What about this?

scope :from_user, lambda{|user|
  joins('left join user_simulations us ON (us.simulation_id = simulations.id)').
  joins('left join group_simulations gs ON (gs.simulation_id = simulations.id)').
  where("us.user_id = ? OR gs.group_id IN (?)",
        user.id,
        UserGroup.select("group_id").where(user_id: user.id))}

Simulation.from_user(user).to_sql:

"SELECT `simulations`.* FROM `simulations` 
left join user_simulations us ON (us.simulation_id = simulations.id)
left join group_simulations gs ON (gs.simulation_id = simulations.id) 
WHERE (us.user_id = 1 OR gs.group_id IN (
  SELECT `user_groups`.`group_id` FROM `user_groups` 
  WHERE `user_groups`.`user_id` = 1))"