Group aggregation with sql_big_result returns wrong result on Spider

CREATE TABLE t3 (

  spID int(10) unsigned,

  userID int(10) unsigned,

  score smallint(5) unsigned,

  key (spid),

  key (score)

)ENGINE=SPIDER COMMENT='wrapper "mysql", table "t3"'

PARTITION BY LIST (spID%2)

(

    PARTITION pt0 VALUES IN (0) COMMENT = 'database "test1_0", table "t3", server "SPT0"',

    PARTITION pt1 VALUES IN (1) COMMENT = 'database "test1_1", table "t3", server "SPT1"'

);

INSERT INTO t3 VALUES

(1,1,1),(2,2,2),(2,1,1),(3,3,3),(4,3,3),(5,3,3),(6,3,3),(7,3,3);

select sql_big_result spid,sum(userid) from t3 group by spid

desc; --bug

select sql_big_result spid,sum(userid) from t3 group by spid

    -> desc;

+------+-------------+

| spid | sum(userid) |

+------+-------------+

|    7 |           3 |

|    6 |           3 |

|    5 |           3 |

|    4 |           3 |

|    3 |           3 |

|    2 |           2 | --> sum(userid) should be 3 here!

|    1 |           1 |

+------+-------------+

7 rows in set (0.20 sec)