Got incorrect result when using hash join

[zyguan]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

drop table if exists t1, t2;
create table t1 ( c_int int, c_decimal decimal(12, 6), key(c_int), unique key(c_decimal) );
create table t2 like t1;
insert into t1 (c_int, c_decimal) values (1, 4.064000), (2, 0.257000), (3, 1.010000);
insert into t2 (c_int, c_decimal) values (1, 4.064000), (3, 1.010000);
select /*+ INL_MERGE_JOIN(t1,t2) */  * from t1 join t2 on t1.c_decimal = t2.c_decimal order by t1.c_int;
select /*+ HASH_JOIN(t1,t2) */  * from t1 join t2 on t1.c_decimal = t2.c_decimal order by t1.c_int;

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

+-------+-----------+-------+-----------+
| c_int | c_decimal | c_int | c_decimal |
+-------+-----------+-------+-----------+
|     1 |  4.064000 |     1 |  4.064000 |
|     3 |  1.010000 |     3 |  1.010000 |
+-------+-----------+-------+-----------+

3. What did you see instead (Required)

mysql> select /*+ INL_MERGE_JOIN(t1,t2) */  * from t1 join t2 on t1.c_decimal = t2.c_decimal order by t1.c_int;
+-------+-----------+-------+-----------+
| c_int | c_decimal | c_int | c_decimal |
+-------+-----------+-------+-----------+
|     1 |  4.064000 |     1 |  4.064000 |
|     3 |  1.010000 |     3 |  1.010000 |
+-------+-----------+-------+-----------+
2 rows in set (0.09 sec)

mysql> select /*+ HASH_JOIN(t1,t2) */  * from t1 join t2 on t1.c_decimal = t2.c_decimal order by t1.c_int;
+-------+-----------+-------+-----------+
| c_int | c_decimal | c_int | c_decimal |
+-------+-----------+-------+-----------+
|     1 |  4.064000 |     1 |  4.064000 |
|     2 |  0.257000 |     3 |  1.010000 |
|     3 |  1.010000 |     3 |  1.010000 |
+-------+-----------+-------+-----------+
3 rows in set (0.06 sec)

4. What is your TiDB version? (Required)

master @ 8978773
release-4.0 @ 7cac557