alter last partition failed when partition column is datetime

[crazycs520]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t (id int, create_time datetime)
		partition by range columns (create_time)
		interval (1 day)
		first partition less than ('2023-01-01')
		last partition less than ('2023-12-31');

alter table t last partition less than ('2024-01-01');

2. What did you expect to see? (Required)

execute success.

3. What did you see instead (Required)

got error:

> alter table t last partition less than ('2024-01-01');
(8200, 'Unsupported LAST PARTITION, does not seem like an INTERVAL partitioned table')

4. What is your TiDB version? (Required)

tidb_version() | Release Version: v7.6.0-alpha-252-g3ed7732958
Edition: Community
Git Commit Hash: 3ed7732958bde87c200e0888a8e7268499b6a115
Git Branch: master
UTC Build Time: 2023-11-22 12:10:03
GoVersion: go1.21.0
Race Enabled: false
Check Table Before Drop: false
Store: unistore