mastodon/db/migrate/20180410220657_create_bookmarks.rb

class CreateBookmarks < ActiveRecord::Migration[5.1]
  def change
    create_table :bookmarks do |t|
      t.references :account, null: false
      t.references :status, null: false

      t.timestamps
    end

    add_foreign_key :bookmarks, :accounts, column: :account_id, on_delete: :cascade
    add_foreign_key :bookmarks, :statuses, column: :status_id, on_delete: :cascade
    add_index :bookmarks, [:account_id, :status_id], unique: true
  end
end