Easiest way to do this is using the FieldCache. It constructs a StringIndex object which gives you very fast lookup to the field value (index) given a docid. Create a parallel count array to the lookup array for the StringIndex. Run your HitCollector thru should be fast. Loading FieldCache maybe expensive, but you do it only once when opening the reader.
This is one way of implementing Faceted Search with Lucene but there are lotsa things you can do to make this faster. This is of course assuming your Brand field is indexed and not tokenized. One side-benefit is that if you do this, sorting on Brand would be fast because FieldCache would be already loaded. Hope this helps -John On Thu, Dec 4, 2008 at 3:02 PM, Muralidharan V <[EMAIL PROTECTED]>wrote: > We are evaluating lucene for a product search engine. One requirement is > that we be able to suggest the top n brands(the ones with most products in > the result set) for a given search term to further refine the search query. > The brand is stored in a separate field and searches are performed against > product description and brand. > > One option is to use a custom HitCollector to keep track of the brands in > the result set but that would require reading the brand field for each doc > that matches the search term. We think this will be an order of magnitude > slower. Is there anything else that we can do? > > Thanks, > Murali >
