Terrible performance for range searches

[Alex Neth]

I am trying to switch from Ferret to Solr.  My searches were  
performing quite well on Ferret (<100ms), but I have some reasons for  
switching.

I am not experiencing terrible performance when doing range searches.   
I have seen posts that granularity should be reduced, but this is not  
an option in my case.

I have around 120K records with 8 digit range integer fields.  When I  
search for a small range, e.g. [0 100] the search is slow, but  
usable.  When I use a larger range, e.g. [0 99999999] the search can  
take over 60 seconds.  Searches without ranges are fast.

Is there a way to get good performance in this case?  This is a  
critical function for my application and I will not be able to use  
Solr unless I can find a way to make this work.

Thanks for any advice.