# File lib/active_record/connection_adapters/mysql2_adapter.rb, line 508
      def pk_and_sequence_for(table)
        keys = []
        result = execute("describe #{quote_table_name(table)}")
        result.each(:symbolize_keys => true, :as => :hash) do |row|
          keys << row[:Field] if row[:Key] == "PRI"
        end
        keys.length == 1 ? [keys.first, nil] : nil
      end