db.Range() is too slow

[nicewook]

I stored 1,000,000 logs to bolt db using storm.
then I tried to use db.Range for time.Time field (using index)

1. it is very slow. around 20-40 seconds for Limit(10000)
2. if the range is not fulfill 10000 records, it seems to search the whole data.

Question. is it normal behavior? or I can improve in some way. I think it is because of db.Range not using index

I am not sure here is the right place to ask. if not, sorry about it