create table `t1`(`a` longtext)engine=innodb charset=utf8; insert into `t1` values (repeat('a',@@global.max_allowed_packet)); insert into `t1` values (repeat('b',@@global.max_allowed_packet)); --error 1054 explain extended select distinct 1 from `t1`, (select distinctrow `a` as `away` from `t1` group by `a` with rollup) as `d1` where `t1`.`a` = `d1`.`a`; drop table `t1`;