Wrong result for UNION query with GROUP BY consisting of PK columns

create table t1(i int primary key disable rely, j int);
insert into t1 values(1,100),(2,200);
create table t2(i int primary key disable rely, j int);
insert into t2 values(2,1000),(4,500);

select i from (select i, j from t1 union all select i,j from t2) subq group by i,j;

HiveAggregate(group=[{0}])
  HiveProject(i=[$0], j=[$1])
    HiveUnion(all=[true])
      HiveProject(i=[$0], j=[$1])
        HiveTableScan(table=[[default, t1]], table:alias=[t1])
      HiveProject(i=[$0], j=[$1])
        HiveTableScan(table=[[default, t2]], table:alias=[t2])