order active_admin column by parent item in belongs_to relationship - ruby-on-rails

Question

I have two models: show_request and show. A show_Request belongs_to a show and a show has_many show_requests. On the show_request page in active_admin, I want to order show_requests by the show's created_at value. Here is my code so far:
ActiveAdmin.register ShowRequest do
controller do
def scoped_collection
end_of_association_chain.includes(:show)
#I also tried ShowRequest.includes(:show)
end
end
index do
column 'Show', sortable: "shows.created_at_asc" do |show_req|
link_to show_req.show.name, admin_show_path(show_req.show)
end
end
end
Here are the server logs:
Started GET "/admin/show_requests" for 127.0.0.1 at 2015-09-18 09:35:36 -0400
Processing by Admin::ShowRequestsController#index as HTML
AdminUser Load (0.3ms) SELECT "admin_users".* FROM "admin_users" WHERE "admin_users"."id" = 1 ORDER BY "admin_users"."id" ASC LIMIT 1
(1.2ms) SELECT COUNT(*) FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't')
(0.2ms) SELECT COUNT(*) FROM "show_requests"
(0.2ms) SELECT COUNT(*) FROM "show_requests" WHERE (not_going_to_show = 't' AND i_want_my_horse_to_compete = 'f')
(0.3ms) SELECT COUNT(count_column) FROM (SELECT 1 AS count_column FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't') LIMIT 30 OFFSET 0) subquery_for_count
CACHE (0.0ms) SELECT COUNT(count_column) FROM (SELECT 1 AS count_column FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't') LIMIT 30 OFFSET 0) subquery_for_count
CACHE (0.0ms) SELECT COUNT(*) FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't')
CACHE (0.0ms) SELECT COUNT(count_column) FROM (SELECT 1 AS count_column FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't') LIMIT 30 OFFSET 0) subquery_for_count
ShowRequest Load (2.0ms) SELECT "show_requests".* FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't') ORDER BY "show_requests"."id" desc LIMIT 30 OFFSET 0
Show Load (9.7ms) SELECT "shows".* FROM "shows" WHERE "shows"."id" IN (2, 1)
User Load (0.4ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1 [["id", 2]]
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1 [["id", 1]]
CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1 [["id", 1]]
Show Load (0.2ms) SELECT "shows".* FROM "shows"
User Load (0.2ms) SELECT "users".* FROM "users"
This is not working. It is not affecting the order of the columns at all. How do I fix this?

Answer 1

Take a look at this part of the log:
ShowRequest Load (2.0ms) SELECT "show_requests".* FROM "show_requests" WHERE (not_going_to_show = 'f' OR i_want_my_horse_to_compete = 't') ORDER BY "show_requests"."id" desc LIMIT 30 OFFSET 0
Show Load (9.7ms) SELECT "shows".* FROM "shows" WHERE "shows"."id" IN (2, 1)
You can see that the ShowRequests and Shows are loaded in separate queries. sortable is not going to work here, because you can't order one table by a field of another without a join. The fix should be to tell ActiveRecord that you need to reference the shows table in your query:
controller do
def scoped_collection
super.includes(:show).references(:shows)
end
end
index do
column :show, sortable: 'shows.created_at'
end
references only works with includes, and forces Rails to perform a join when eager loading.