`insert on duplicate` with global index report `key not exists`

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

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

Run SQL below

insert into t values (1, 1), (1, 2) on duplicate key update a=1, b=3;

Or

insert into t values (1, 1);
insert into t values (1, 2) on duplicate key update a=1, b=3;

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

no error

3. What did you see instead (Required)

report ERROR 8021 (HY000): Error: key not exist

4. What is your TiDB version? (Required)