ransack_bug_demo.rb

begin
  require "active_record" # 4.2.4
  require "ransack" # 1.6.6
  require "sqlite3" # 1.3.11
rescue LoadError
  warn "⚠️  Install the activerecord, ransack, and sqlite3 gems first."
  exit
end

ActiveRecord::Base.establish_connection(
  adapter: "sqlite3",
  database: ":memory:"
)

ActiveRecord::Migration.verbose = false

ActiveRecord::Schema.define do
  create_table :authors, force: true do |t|
  end

  create_table :authorships, force: true do |t|
    t.integer :author_id
    t.integer :post_id
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
    t.datetime :created_at
  end

  create_table :posts, force: true do |t|
  end
end

class Author < ActiveRecord::Base
  has_many :authorships
  has_many :posts, through: :authorships
end

class Authorship < ActiveRecord::Base
  belongs_to :author
  belongs_to :post
end

class Post < ActiveRecord::Base
  has_many :authorships
  has_many :authors, through: :authorships
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

author_1 = Author.create!(id: 1)
author_2 = Author.create!(id: 2)

post_1 = Post.create!(id: 1, authors: [author_1])
post_2 = Post.create!(id: 2, authors: [author_1])
post_3 = Post.create!(id: 3, authors: [author_2])
post_4 = Post.create!(id: 4, authors: [author_2])

Comment.create!(id: 1, post: post_1, created_at: 4.days.ago)
Comment.create!(id: 2, post: post_1, created_at: 2.days.ago)
Comment.create!(id: 3, post: post_2, created_at: 4.days.ago)
Comment.create!(id: 4, post: post_2, created_at: 2.days.ago)
Comment.create!(id: 5, post: post_3, created_at: 4.days.ago)
Comment.create!(id: 6, post: post_3, created_at: 2.days.ago)
Comment.create!(id: 7, post: post_4, created_at: 4.days.ago)
Comment.create!(id: 8, post: post_4, created_at: 2.days.ago)

relation = Post.
  joins(:authors).
  ransack(
    # Swap the following two lines:
    comments_created_at_gteq: 3.days.ago,
    authors_id_eq: author_1.id,
  ).
  result

begin
  relation.to_a
rescue
  puts "💣  Invalid SQL!"
else
  puts "👍  All is well."
end