mozilla/elasticutils — pull request #217 by mihneadb (2014-03-06 21:02:07+00:00)
Title: Do not set facet_filter if there is no filter.

I stumbled across this issue when calling .facet(..., filtered=True) on a query that did not have a filter. I'd say that the API should be robust and accept this usecase, especially since you can set up a pipeline that chains various calls on an S() object and ends up calling facet on it.