select count(aa.delete_flag) from (
select e.delete_flag
from exercise e
where? 1=1
and e.lib_id='808080aa3f7639b7013f7a1010cf0012'
and e.owner_id = 'ff8080813ec7d82f013ecb13f9d90237'
and e.delete_flag =0
) aa;

?

exercise表有100万,ower_id,lib_id,delete_flag建了联合索引