On Fri, 12 Aug 2011 00:02:09 +0200, Sanne Grinovero <sanne(a)hibernate.org&gt; wrote: It was attached to the original Lucene issue related to faceting. Yeah, there are quite some rules around when to commit in relation to the main index writer. Good that there is Hibernate Search which can handle this for the user :-) Personally I am surprised that they introduced this new taxonomy index. Funny enough the actual indexed Documents also contain category (faceting) information. Hence also the need for the DocumentBuilder. I am sure that there are good reasons to introduce this new index, but I am surprised nevertheless. I want to expose as little as possible of the underlying Lucene functionality. For power users we might want to offer some way to access the TaxonomyIndex/Reader directly. Not sure yet. We will also need to extend on the annotation side. Our approach allows to facet on any un-tokenized field. In the Lucene case we need to know for which fields we have to create faceting information. We could do this with an additional optional parameter to @Field or we introduce a new @Faceted (or something like this) annotation. Obviously the Lucene goes a step further with category path than our current faceting approach, but we don't have to extend our faceting DSL right away. For clustering purposes I think we have to look at CategoryPath and how to serialize it. It should be just a bunch of strings, but I haven't seen the code yet. It would have been nice to get this stuff into Search 4 as well, but of course it depends on when the next version of Lucene (either 3.4 or 4) would be available. A Hibernate Search 4 bundled w/ Hibernate Core 4 and Lucene 4 would have been cool, but I don't think the timing will work out :-) --Hardy