agg query result error on single tablet table

[silverbullet233]

Steps to reproduce the behavior (Required)

1. create table and insert data

create table t (
  `c0` int,
  `c1` int,
  `c2` int
) engine=OLAP
primary key(`c0`)
distributed by hash(`c0`) buckets 1
properties("replication_num"="1");
insert into t values (1,1,1),(2,2,2),(3,3,1),(4,4,2);

2. query and get a wrong result

mysql> set pipeline_dop=2;
Query OK, 0 rows affected (0.00 sec)

mysql> select c2,count(distinct c1,c2) from t group by c2;
+------+------------------------+
| c2   | count(DISTINCT c1, c2) |
+------+------------------------+
|    2 |                      1 |
|    1 |                      2 |
|    2 |                      1 |
+------+------------------------+
3 rows in set (0.01 sec)

Expected behavior (Required)

mysql> select c2,count(distinct c1,c2) from t group by c2;
+------+------------------------+
| c2   | count(DISTINCT c1, c2) |
+------+------------------------+
|    1 |                      2 |
|    2 |                      2 |
+------+------------------------+
2 rows in set (0.01 sec)

Real behavior (Required)

StarRocks version (Required)

mysql> select current_version();
+-------------------+
| current_version() |
+-------------------+
| main-43db8fe |
+-------------------+
1 row in set (0.01 sec)