Say I have a facet on countries, I'd like to be able to click on more than one country (say US and UK) and get results tagged "US" OR "UK".
Currently If I click on "UK" on the facet block, the other terms disappear if this was a "single solr field".
And if it was a multi-valued solr field, the other terms don't disappear but an AND operation is done.
How can I change the default behavior to allow OR operation on both "single" and "multi-valued" solr fields?
I'm using the Apache Solr Search Integration module version 1.6.