[sqlite] Is this query optimized?

[R S]

Hi,
I am trying to use this query and notice that the execution time increasing
linearly as the Table size increases.

select totalCount from (select count(*) as totalCount from myTable where
(insertionTime BETWEEN <beginTime> and <endTime>) and columnVal > '0' group
by columnVal) where totalCount > 10;

Diff between beginTime and endTime is always constant.
columnVal is a varchar.
aColumn is an integer.

Thanks!