ruby on rails - How do I eliminate multiple joins of the same table in a has_many through association with multiple scopes? -

given following models , associations:

class employee    has_many :positions    has_many :titles, :through => :positions    scope :is_active, -> { joins(:positions).merge(position.is_active) }    scope :title_is, ->(name) { joins(:titles).merge(title.id_or_name_is(name)) } end  class position    belongs_to :employee    belongs_to :title    # bool 'active' indicate whether position active or not    scope :is_active, -> { where("active = true") } end  class title    has_many :positions    has_many :employees, :through => :positions    scope :id_or_name_is, ->(id_or_name) { where("titles.id = ? or titles.name = ?", id_or_name, id_or_name) if id_or_name} end 

employee.is_active returns correct number of results , generates correct query. however, when attempt employee.title_is(123).is_active (which want return employees title_id 123 , active, results in multiple joins position. no problem except active check applies 1 of position joins thereby resulting in both active positions , inactive positions:

select count(*) `employees`     inner join `positions` on `positions`.`employee_id` = `employees`.`id`     inner join `positions` `positions_employees_join` on positions_employees_join`.`employee_id` = `employees`.`id`     inner join `titles` on titles`.`id` = `positions_employees_join`.`title_id`  positions.active = true)       , (titles.id = 123 or        titles.name = 123) 

i should note technically if had way of adding in clause positions_employees_join.active = true, work correctly well, though don't know how in scope.

i skip using titles association in title_is scope.

scope :title_is, ->(name) { joins(:positions => :title).merge(title.is_or_name_is(name)) } 

keep association because still gives more efficient queries when calling employee_instance.titles rather employee_instance.positions.titles.

but purpose of scope, doing joins(:positions => :title) tells activerecord want use regular join other scopes call joins(:positions).