# frozen_string_literal: true

class AddUniqueIndexToForumThreadLinks < ActiveRecord::Migration[4.2]
  def change
    execute "DELETE FROM forum_thread_links USING forum_thread_links ftl2
              WHERE ftl2.forum_thread_id = forum_thread_links.forum_thread_id
                              AND ftl2.post_id = forum_thread_links.post_id
                              AND ftl2.url = forum_thread_links.url
                              AND ftl2.id < forum_thread_links.id"

    # Add the unique index
    add_index :forum_thread_links,
              %i[forum_thread_id post_id url],
              unique: true,
              name: "unique_post_links"
  end
end