We should set the `size` on the facet field as described [here](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-facets-terms-facet.html). Probably to something like `1000`. Elasticsearch doesn't include all the results in the facets in order to make the queries go faster. By default it'll only return the top 10 facets, and add a `other` count field to say how many other facet terms were excluded. The trick to get everything is to just repeat the query with a larger size until `other` is 0. I don't think it's important to do that now, but I'll add an issue to get that done in the future if we have more free time. Defaulting to a large size is fine for now.