SET @@sql_mode = '';

CREATE TABLE series (

  val INT(10) UNSIGNED NOT NULL

);

INSERT INTO series VALUES(1);

CREATE TABLE seq_calls (

  c INT

);

INSERT INTO seq_calls VALUES(0);

DELIMITER |;

CREATE FUNCTION next_seq_value() RETURNS INT

BEGIN

 DECLARE next_val INT;

 SELECT val INTO next_val FROM series;

 UPDATE series SET val=mod(val + 1, 2);

 UPDATE seq_calls SET c=c+1;

 RETURN next_val;

END;

|

DELIMITER ;|

CREATE TABLE t1 (t INT, u INT, KEY(t));

INSERT INTO t1 VALUES(10, 10), (11, 11), (12, 12), (12, 13),(14, 15), (15, 16),

                     (16, 17), (17, 18);

ANALYZE TABLE t1;

SELECT * FROM series, seq_calls;

SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t)

GROUP BY t HAVING (SELECT 1 FROM t1 WHERE r = 1 LIMIT 1)

ORDER BY t1.u;

DROP TABLE t1;

DROP FUNCTION next_seq_value;

DROP TABLE series, seq_calls;

MariaDB [test]> SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t)

    -> GROUP BY t HAVING (SELECT 1 FROM t1 WHERE r = 1 LIMIT 1)

    -> ORDER BY t1.u;

+------+------+

| t    | r    |

+------+------+

|   10 |    1 |

|   11 |    1 |

|   12 |    1 |

|   14 |    1 |

|   15 |    1 |

|   16 |    1 |

|   17 |    1 |

+------+------+

MariaDB [test]> SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t)

    -> GROUP BY t HAVING (SELECT 1 FROM t1 WHERE r = 1 LIMIT 1)

    -> ORDER BY t1.u;

+------+------+

| t    | r    |

+------+------+

|   10 |    1 |

|   12 |    1 |

|   15 |    1 |

|   17 |    1 |

+------+------+