Solr facet counts for specific field values

Question

Solr creates multi-select facet counts for me as described here:

https://web.archive.org/web/20131202095639/http://wiki.apache.org/solr/SimpleFacetParameters#Multi-Select_Faceting_and_LocalParams

I also have various predefined searches that allow a user to browse the catalog. Here is one such example and its query parameters:

q=*:*
fq={!tag=g}genre:western
facet=on
facet.field={!ex=g}genre
facet.mincount=1
facet.limit=50

With this search I get up to 50 genre values in the facet list. I then go through and mark which values were selected by the user; western in this case. This works well except when western is pushed out of the top 50. So I manually add it to the list to make a total of 51. This way the user can see that it is indeed selected. The problem is I have to leave the count for western blank because I don't know it.

Is there a way to get counts for specific facet values such as western in this case? Or another approach to solve this issue?

I am using Solr 4.7.0.

Answer 1

Solr allows you to create a query-based facet count by using the facet.query parameter. When creating a filter query (fq) that's based on a facet field value, I now create a corresponding facet query:

facet.query={!ex=g}genre:western

and add it to the rest of my parameters:

q=*:*
fq={!tag=g}genre:western
facet=on
facet.field={!ex=g}genre
facet.query={!ex=g}genre:western
facet.mincount=1
facet.limit=50

The facet_queries object will now be populated in the solr response:

{
  ...
  "facet_counts": {
    "facet_queries": {
      "{!ex=g}genre:western": 7
    },
    ...
  },
  ...
}

Regardless of what is returned in the facet_fields object, I'm now guaranteed to have a facet count for genre:western. With some parsing, facet field counts can be extracted from the facet queries.