zacachovaný result

CREATE TABLE `session` (
  `id` varchar(255) NOT NULL,
  `data` text NOT NULL,
  `createdTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `locked` timestamp NULL DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

DELIMITER ;;
CREATE FUNCTION `getSession` (`sessionId` varchar(255) CHARACTER SET 'utf8', `waitingTime` int) RETURNS text CHARACTER SET 'utf8'
BEGIN

    DECLARE lockedSession TIMESTAMP;
    DECLARE lockExpire int;
    DECLARE result text;
    DECLARE i float;
    DECLARE sleepInterval float;
    DECLARE sleepStatus int;
    DECLARE isExist int;


    SET i = 0;
    SET sleepInterval = 0.2; -- seconds --
    SET lockExpire = 60; -- seconds --


    SELECT data, locked, count(*) into result, lockedSession, isExist FROM session WHERE id = sessionId;


    IF( isExist = 0) THEN
        RETURN result;
    END IF;


    IF( lockedSession IS NULL || ABS(TIMEDIFF(lockedSession , NOW())) > lockExpire  ) THEN
        UPDATE session SET locked = NOW() WHERE id = sessionId;
        SELECT data into result FROM session WHERE id = sessionId;
        RETURN result;
    END IF;


    WHILE (i < waitingTime) DO
        SELECT SQL_NO_CACHE data, locked, count(*) into result, lockedSession, isExist FROM session WHERE id = sessionId;

        IF(lockedSession IS NULL) then
            RETURN result;
        END IF;

        SELECT SLEEP(sleepInterval) into sleepStatus ;
        SET i = i + 1 * sleepInterval ;
    END WHILE;
 

    RETURN FALSE;

END;;
DELIMITER ;