Poor speed with many records and sorting

[ollehints]

If browsing 1 M records, solr is very fast in showing the first pages, but slows considerably in the end of records. Compare:

http://geocase.geocollections.info/api/?start=10&rows=10&sort=fullscientificname%20asc&defType=edismax&q=* 
http://geocase.geocollections.info/api/?start=100000&rows=10&sort=fullscientificname%20asc&defType=edismax&q=* 

This seems to be related to sorting. Maybe the problem appeared after changing the field from string to text?

[enmust]

Tested and it even gets worse if rows is 25 or higher. For some cases the time was almost 10 seconds.
It does indeed get slower in the end of records even when sorting by other fields but fullscientificname seems to be extra slow.