ActiveRecord error occurs in a controller only, see StackOverflow question: http://stackoverflow.com/questions/6919133/sort-a-query-based-on-an-association-2-or-more-levels-deep/6932985#6932985

gistfile1.txt

# the following line will cause this error in my controller
# @post = Post.includes(:user, :subtopic => :category).paginate(:page =>1, :order => 'categories.category_name ASC', :conditions => ["posts.flags_count < ?", Flag.flag_threshold])


Hirb Error: PGError: ERROR:  column posts.users.display_name does not exist
LINE 1: ...s_count" AS t0_r7, "posts"."popularity" AS t0_r8, "posts"."u...
                                                             ^
: SELECT  "posts"."id" AS t0_r0, "posts"."post_content" AS t0_r1, "posts"."user_id" AS t0_r2, "posts"."subtopic_id" AS t0_r3, "posts"."created_at" AS t0_r4, "posts"."updated_at" AS t0_r5, "posts"."votes_count" AS t0_r6, "posts"."flags_count" AS t0_r7, "posts"."popularity" AS t0_r8, "posts"."users.display_name" AS t0_r9, "posts"."subtopics.name" AS t0_r10, "posts"."categories.category_name" AS t0_r11, "users"."id" AS t1_r0, "users"."email" AS t1_r1, "users"."encrypted_password" AS t1_r2, "users"."password_salt" AS t1_r3, "users"."reset_password_token" AS t1_r4, "users"."remember_token" AS t1_r5, "users"."remember_created_at" AS t1_r6, "users"."sign_in_count" AS t1_r7, "users"."current_sign_in_at" AS t1_r8, "users"."last_sign_in_at" AS t1_r9, "users"."current_sign_in_ip" AS t1_r10, "users"."last_sign_in_ip" AS t1_r11, "users"."created_at" AS t1_r12, "users"."updated_at" AS t1_r13, "users"."display_name" AS t1_r14, "users"."posts_count" AS t1_r15, "users"."admin" AS t1_r16, "subtopics"."id" AS t2_r0, "subtopics"."name" AS t2_r1, "subtopics"."category_id" AS t2_r2, "subtopics"."flags_count" AS t2_r3, "subtopics"."alterable" AS t2_r4, "subtopics"."created_at" AS t2_r5, "subtopics"."updated_at" AS t2_r6, "subtopics"."user_id" AS t2_r7, "subtopics"."posts_count" AS t2_r8, "categories"."id" AS t3_r0, "categories"."category_name" AS t3_r1, "categories"."created_at" AS t3_r2, "categories"."updated_at" AS t3_r3 FROM "posts" LEFT OUTER JOIN "users" ON "users"."id" = "posts"."user_id" LEFT OUTER JOIN "subtopics" ON "subtopics"."id" = "posts"."subtopic_id" LEFT OUTER JOIN "categories" ON "categories"."id" = "subtopics"."category_id" WHERE (posts.flags_count < 5) ORDER BY categories.category_name ASC LIMIT 30 OFFSET 0
    /home/eric/.rvm/gems/ruby-1.8.7-p352@global/gems/activerecord-3.0.9/lib/active_record/connection_adapters/abstract_adapter.rb:207:in `log'
    /home/eric/.rvm/gems/ruby-1.8.7-p352@global/gems/activerecord-3.0.9/lib/active_record/connection_adapters/postgresql_adapter.rb:514:in `execute'
    /home/eric/.rvm/gems/ruby-1.8.7-p352@global/gems/activerecord-3.0.9/lib/active_record/connection_adapters/postgresql_adapter.rb:1004:in `select_raw'
    /home/eric/.rvm/gems/ruby-1.8.7-p352@global/gems/activerecord-3.0.9/lib/active_record/connection_adapters/postgresql_adapter.rb:997:in `select'