executor: index merge has wrong result for global index

[L-maple]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

set session tidb_enable_index_merge = on;
drop table if exists p;
create table p (id int, c int, d int) partition by range (c) (
partition p0 values less than (4),
partition p1 values less than (7),
partition p2 values less than (10)
);
alter table p add unique idx_id(id);
alter table p add unique idx_c(c);
insert into p values (1, 1, 1), (2, 2, 2), (3, 3, 3);
SELECT /*+ USE_INDEX_MERGE(p)*/ * FROM p WHERE id = 1 OR c = 2;

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

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

-------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version() |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v7.1.0-alpha-144-g7d28afc3fe
Edition: Community
Git Commit Hash: 7d28afc3fe8e709861759ea96327bb9458e07a32
Git Branch: local/enhance_ddl_for_global_index_v4
UTC Build Time: 2023-04-14 09:12:14
GoVersion: go1.20.2
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: unistore |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[Defined2014]

duplicate with #43013, so close this one