Can create global index with partition columns

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a int, b int) partition by hash(b) partitions 5;
alter table t add unique idx(b) global;

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

report error

3. What did you see instead (Required)

alter global index success

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                           |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v8.2.0-alpha-869-g1b172b674f
Edition: Community
Git Commit Hash: 1b172b674fa37259fabc4fcbc205274d4091fcce
Git Branch: master
UTC Build Time: 2024-08-15 03:11:41
GoVersion: go1.23.0
Race Enabled: false
Check Table Before Drop: false
Store: unistore |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[Defined2014]

And also SQL below

create table t(a int, b int, unique index idx(a) global);