Range partition: allow ADD PARTITION into the middle of ranges list

create or replace table t1 (x int)

partition by range columns (x) (

  partition p0 values less than (10),

  partition p1 values less than (20),

  partition pn values less than maxvalue);

insert into t1 values (1);

insert into t1 values (11);

insert into t1 values (31);

alter table t1 add partition (partition p2 values less than (30));

alter table t1 add partition (partition p2 values less than (30));

ERROR 1493 (HY000): VALUES LESS THAN value must be strictly increasing for each partition

create or replace table t1 (x int)

partition by range columns (x) (

  partition p0 values less than (10),

  partition p1 values less than (20),

  partition pn values less than maxvalue);

insert into t1 values (1);

insert into t1 values (11);

insert into t1 values (31);

alter table t1 convert partition pn to table pn;

alter table t1 add partition (partition p2 values less than (30));

alter table t1 convert table pn to partition pn values less than maxvalue;

CREATE TABLE `t1` (

  `x` int(11) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci

 PARTITION BY RANGE  COLUMNS(`x`)

(PARTITION `p0` VALUES LESS THAN (10) ENGINE = InnoDB,

 PARTITION `p1` VALUES LESS THAN (20) ENGINE = InnoDB,

 PARTITION `p2` VALUES LESS THAN (30) ENGINE = InnoDB,

 PARTITION `pn` VALUES LESS THAN (MAXVALUE) ENGINE = InnoDB)

create or replace table t1 (x int)

partition by range columns (x) (

  partition p0 values less than (10),

  partition p1 values less than (20),

  partition pn values less than maxvalue);

insert into t1 values (21);

alter table t1 add partition (partition p2 values less than (30));

create or replace table t1 (x int)

partition by range columns (x) (

  partition p0 values less than (10),

  partition p1 values less than (20),

  partition pn values less than maxvalue);

insert into t1 values (21);

alter table t1 convert partition pn to table pn;

alter table t1 add partition (partition p2 values less than (30));

alter table t1 convert table pn to partition pn values less than maxvalue;

alter table t1 convert table pn to partition pn values less than maxvalue;

ERROR 1737 (HY000): Found a row that does not match the partition