mastodon/db/migrate/20171116161857_create_list_accounts.rb

class CreateListAccounts < ActiveRecord::Migration[5.1]
  def change
    create_table :list_accounts do |t|
      t.belongs_to :list, foreign_key: { on_delete: :cascade }, null: false
      t.belongs_to :account, foreign_key: { on_delete: :cascade }, null: false
      t.belongs_to :follow, foreign_key: { on_delete: :cascade }, null: false
    end

    add_index :list_accounts, [:account_id, :list_id], unique: true
    add_index :list_accounts, [:list_id, :account_id]
  end
end