Searching for negative numbers very slow

[Simon Wistow]

If I do 

        qt=dismax
    fq=uid:1

(or any other positive number) then queries are as quick as normal - in 
the 20ms range. 

However, any of

        fq=uid:\-1

or

    fq=uid:[* TO -1]

or 
   
    fq=uid:[-1 to -1]

or

    fq=-uid:[0 TO *]

then queries are incredibly slow - in the 9 *second* range.

Anything I can do to mitigate this? Negative numbers have significant 
meaning in our system so it wouldn't be trivial to shift all uids up by 
the number of negative ids.


Thanks, 

Simon