if I change mdev_29008.test to use ORDER BY without aliases to an aggregate function, like

SELECT MIN(t2.a) AS f1, t1.b AS f2 FROM tbl_a AS t1 JOIN tbl_a AS t2 GROUP BY f2 ORDER BY MIN(t2.a), MAX(t2.a), f2;

Then I can see that the spider will generate the query

select max(t1.`a`) ``,min(t1.`a`) ``,min(t1.`a`) `f1`,t0.`b` `b` from `auto_test_remote`.`tbl_a` t0,`auto_test_remote`.`tbl_a` t1 group by t0.`b` order by ``,``,t0.`b`

which is clearly wrong, it doesn't distinguish between min and max. It needs to auto-generate names for aggregates as needed.

Also might apply to HAVING