使用Lucene计算类别中的结果

I am trying to use Lucene Java 2.3.2 to implement search on a catalog of products. Apart from the regular fields for a product, there is field called 'Category'. A product can fall in multiple categories. Currently, I use FilteredQuery to search for the same search term with every Category to get the number of results per category.I am trying to use Lucene Java 2.3.2 to impleme