Faceting is a hugely important feature, available in Solr today but
not [easily] usable by Lucene-only apps.
We should fix this, by creating a shared faceting module.
Ideally, we factor out Solr's faceting impl, and maybe poach/merge
from other impls (eg Bobo browse).
Hoss describes some important challenges we'll face in doing this
(http://markmail.org/message/5w35c2fr4zkiwsz6), copied here:
This is a great list of the things we face in refactoring. It's also
important because, if Solr needed to be so deeply intertwined with
caching, schema, etc., other apps that want to facet will have the
same "needs" and so we really have to address them in creating the
I think we should get a basic faceting module started, but should not
cut Solr over at first. We should iterate on the module, fold in
improvements, etc., and then, once we can fully verify that cutting
over doesn't hurt Solr (ie lose functionality or performance) we can