Dabs like product filtering


Im trying to create a search\filtering similar to dabs, see link below. So the "Refine Your Search" menu breaks down the different categories\sub categories for a product with a count of how many are available and you can drill down....

Is there a plugin in rails that makes this easy(ive looked about but nothing seemed to meet this requirment)


is there any advice on how best to do this.

Options maybe to do it dynamically so when a customer searches then get the relevant sub categories and do the counts seperately(this seems intensive and will kill performance as the dataset gets bigger)

Another option may be to do it evytime a new product is added to update a table with counts etc, again this seems a bit overkill as it will need to be done everytime a product is added/edited etc

Any advice appreciated,