[hibernate-dev] [HSearch] Faceting feedback

Hi, I thought it would be great to get some feedback on my faceting work. You can see the latest on my Search fork - https://github.com/hferentschik/hibernate-search/commits/HSEARCH-667 Technically I decided to use a simple custom Collector. I abandoned the idea for using bobo browse, since it did not really seem to fit our architecture and I am not sure how well maintained the code is. Within the custom Collector I am using Lucene's FieldCache to cache and collect the count values during facting (as a reminder, faceting for example means that I am searching for all cars or a certain make, but then also want to group the matching cars into their cubic capacity. See also - http://en.wikipedia.org/wiki/Faceted_search) Using the FieldCache is quite memory costly, but there are other ways to implement the faceting itself. At the moment I am mostly interested in the feedback around the public API. The public classes can be found in the package org.hibernate.search.query.facet - https://github.com/hferentschik/hibernate-search/tree/3a9877e2bbc47a8bd6e... The idea is to write a fulltext query as usual and then add/enable a facet: FacetRequest request = new SimpleFacetRequest( indexFieldName, FacetSortOrder.COUNT_DESC, false ); TermQuery term = new TermQuery( new Term( "make", "honda" ) ); FullTextQuery query = fullTextSession.createFullTextQuery( term, Car.class ); query.enableQueryFacet( "foo", request ); Then you run the query. This will enable the facet collector and after the query executed you get access to a map which maps FacetResults to the facet name. Each FacetResult contains a list of Facets which contain the actually field values and counts: Map<String, FacetResult> results = query.getFacetResults(); FacetResult facetResult = results.get( "foo" ); List<Facet> facetList = facetResult.getFacets(); assertEquals( "Wrong facet count for facet ", 100, facetList.get( 0 ).getCount() ); More actual tests can be found here - https://github.com/hferentschik/hibernate-search/tree/3a9877e2bbc47a8bd6e... At the moment you are able to facet on simple (string) based values or on number ranges (eg price ranges 0 - 100, ...). For that I have created subclasses of FacetRequest - SimpleFacetRequest and RangeFacetRequest (a DateRangeFacetRequest might be interesting as well) Some concrete questions: * Atm, I am only exposing a programmatic API for creating FacetRequests. I guess we want to have annotations for this as well, right? Would we keep the programmatic configuration as a public API? * I made the FacetRequest classes immutable atm, but this way I have a multitude of constructors catering for a whole range of parameters (sort order, include zero counts, ...). Any opinions around immutable objects vs objects with setters for configuring options after creation. If course I am interested in any other feedback as well. --Hardy