Here is a possible option for creating a multiple field search handler in Drupal
The problem:
Say I have a property website and I wanted to to offer users the ability to search on a number of different fields in my Solr index. At the moment in the Solr admin interface you have the ability to put content bias on a number of predefined fields. Whilst useful it doesn't give you very fine grained control.
I have been using the Drupal Apache Solr module since about May 2008 and have seen it evolve into a awsome feature rich module. It is now in a state that it is able to do most of the standard things you need for a client build out of the box including field boosting, more like this and faceted search. The only things I always ended up adding patches for was returning custom fields (to the fl "field list" param) and messing with the results returned from Solr e.g.
