-`cat` CHAR( 255 ) NOT NULL ,
-`k` CHAR( 255 ) NOT NULL ,
-`v` MEDIUMTEXT NOT NULL
+`cat` CHAR( 255 ) CHARACTER SET ascii COLLATE ascii_general_ci NOT NULL ,
+`k` CHAR( 255 ) CHARACTER SET ascii COLLATE ascii_general_ci NOT NULL ,
+`v` MEDIUMTEXT NOT NULL,
+UNIQUE KEY `access`(`cat`, `k`)