I have met this issue.
I have a table t with 3 columns, id1,id2, num.
I am doing this
select a.id2 m, b.id2 n, sum(a.num), sum(b.num)
from t a, t b
where a.id1=b.id1
group by a.id2, b.id2;
the problem is if I don't do the two sums. the speed is quite well.
if I add one of the sums, the speed is still reasonable, but if I add the two sums together, the speed goes down two much, about double time needed.
Anyone can help on this? I think the table is a column one, the calculation of the two sums should be done in parallel, so there should not be so much different in speed.
by the way, I used the 'request_flags'='ANALYZE_MODEL' in the testing. so the real sql is
select a.id2 m, b.id2 n, sum(a.num), sum(b.num)
from t a, t b
where a.id1=b.id1
group by a.id2, b.id2
'request_flags'='ANALYZE_MODEL'
;