Mekin: Yonik has done some brainstorming on ways of supporting "Feterated" searching across multiple instances of Solr - but the main motivation there is to deal with homogeneous indexes which are too big to fit on a single host efficiently...
http://wiki.apache.org/solr/FederatedSearch
..if you've got seperate schemas for each of your indexes, then you have
to query then in different ways, so how could you meaningfully merge the
scores?
-Hoss
