class ActiveRecord::PredicateBuilder::AssociationQueryValue

def convert_to_id(value)
  if value.respond_to?(primary_key)
    value.public_send(primary_key)
  else
    value
  end
end

def ids
  case value
  when Relation
    value.select_values.empty? ? value.select(primary_key) : value
  when Array
    value.map { |v| convert_to_id(v) }
  else
    convert_to_id(value)
  end
end

def initialize(associated_table, value)
  @associated_table = associated_table
  @value = value
end

def primary_key
  associated_table.join_primary_key
end

def queries
  [ associated_table.join_foreign_key => ids ]
end