ttl

获取单行数据的TTL时间。TTL表示Time To Live，表示该数据还能存活多久。如果超过存活时间，数据就读不到了

  1.     ///
  2.     /// \brief ttl (time to live)
  3.     ///     get ttl in seconds of this k-v.
  4.     ///     key is composed of hashkey and sortkey. must provide both to get the value.
  5.     /// \param hashkey
  6.     /// used to decide which partition to get this k-v
  7.     /// \param sortkey
  8.     /// all the k-v under hashkey will be sorted by sortkey.
  9.     /// \param ttl_seconds
  10.     /// the returned ttl value in seconds.
  11.     /// \param timeout_milliseconds
  12.     /// if wait longer than this value, will return time out error
  13.     /// \return
  14.     /// int, the error indicates whether or not the operation is succeeded.
  15.     /// this error can be converted to a string using get_error_string()
  16.     ///
  17.     virtual int ttl(const std::string &hashkey,
  18.                     const std::string &sortkey,
  19.                     int &ttl_seconds,
  20.                     int timeout_milliseconds = 5000,
  21.                     internal_info *info = NULL) = 0;