exist

判断单条数据是否存在

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