Clone, bundle install, rake db:create db:migrate
In rails c:
> p = Post.create!
> u = User.create!
> p.comments.where(user: u.followers)
Comment Load (0.4ms) SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = $1 AND "comments"."user_id" IN (SELECT "users"."id" FROM "users" INNER JOIN "user_relationships" ON "users"."id" = "user_relationships"."follower_id" WHERE "user_relationships"."following_user_id" = $1) [["post_id", 2], ["following_user_id", 2]]
PG::ProtocolViolation: ERROR: bind message supplies 2 parameters, but prepared statement "a1" requires 1