Custom aggregate functions work incorrectly with WITH ROLLUP clause

--delimiter |

create aggregate function agg_sum(x INT) returns INT

begin

declare z int default 0;

declare continue handler for not found return z;

loop

fetch group next row;

set z= z+x;

end loop;

end|

--delimiter ;

create table t1 (i int);

insert into t1 values (1),(2),(2),(3);

select i, agg_sum(i) from t1 group by i with rollup;

--echo #

--echo # Compare with

select i, sum(i) from t1 group by i with rollup;

# Cleanup

drop function agg_sum;

drop table t1;

select i, agg_sum(i) from t1 group by i with rollup;

i	agg_sum(i)

1	1

2	8

3	6

NULL	6

select i, sum(i) from t1 group by i with rollup;

i	sum(i)

1	1

2	4

3	3

NULL	8