执行修改表分区操作时报错

ERROR:start value of partition "XX" NOT EQUAL up-boundary of last partition.

--创建分区表partitiontest。
MogDB=#  CREATE TABLE partitiontest
(
c_int integer,
c_time TIMESTAMP WITHOUT TIME ZONE
)
PARTITION BY range (c_int)
(
partition p1 start(100)end(108),
partition p2 start(108)end(120)
);
--使用如下两种语句会发生报错：
MogDB=#  ALTER TABLE partitiontest ADD PARTITION p3 start(120)end(130), DROP PARTITION p2;
ERROR:  start value of partition "p3" NOT EQUAL up-boundary of last partition.
MogDB=#  ALTER TABLE partitiontest DROP PARTITION p2,ADD PARTITION p3 start(120)end(130);
ERROR:  start value of partition "p3" NOT EQUAL up-boundary of last partition.
--可以修改语句为：
MogDB=#  ALTER TABLE partitiontest ADD PARTITION p3 start(108)end(130), DROP PARTITION p2;
MogDB=#  ALTER TABLE partitiontest DROP PARTITION p2,ADD PARTITION p3 start(108)end(130);