upsert

  def call
    @conn.exec(ERB.new(erb_template).result(binding))
  end

  private

  def post_initialize(_args)
    @conn = Database::Adapter.conn
  end

  def erb_template
    <<-SQL
      <% TABLES.each do |table| %>
        begin transaction;
          delete from <%= table %>
          using <%= table %>_copy
          where
            <%= table %>.id = <%= table %>_copy.id;

          insert into <%= table %>
          select * from <%= table %>_copy;
        end transaction;
      <% end %>
    SQL
  end