With the nested Category structure of uCommerce, I want to have facets for the category being displayed but also to include an child categories. I've tried a couple of approaches, none of which have worked. This is a couple of things I've tried, has anyone got this working before:

var currentCategory = SiteContext.Current.CatalogContext.CurrentCategory;

//get the child category id's and also add the current category Id to the list
var allIds = currentCategory.Categories.Select(x => x.CategoryId).ToList();
allIds.Add(category.CategoryId);

   //attempt 1 using custom Facet Search - throws Raven DB not supported exception
    var facetResults =
                        SearchLibrary.FacetedQuery()
                            .Where(x => x.CategoryIds.Intersect(allIds).Any())
                            .ToFacets()
                            .ToList();
 //attempt 2 with custom facet
 var facet = new Facet();
 facet.FacetValues = new List<FacetValue>();
 facet.Name = "Category";
 facet.DisplayName = facet.Name;
 foreach (var value in allIds)
  {
           facet.FacetValues.Add(new FacetValue() { Value = value.ToString() });
   }
   facets.Add(facet);

   //No results are returned here
  var results = SearchLibrary.FacetedQuery().WithFacets(facets).ToList();