Hi, Nils. We've implemented something like this here at ThingWorx, but we had to do so at a layer above Neo4J since there, of course, were no built-in faceting capabilities. One of the major challenges we faced was the "opaque" connection from the Neo4J API to the underlying Lucene engine. There are quite a few things we would/could have done differently if we could access the underlying Lucene IndexReaders directly, but that isn't possible. Nor would it probably be wise, since Neo4J's indexing framework does a lot of transaction isolation "magic" for Lucene that you'd run the risk of interfering with.
Also, you'll probably find that you need to implement faceting at a higher level anyway, since in Neo4J, the concept of a "document" in an index is merely its node or relationship ID - not the set of properties associated with it, so you'll need to do most of that work of reconstituting a document-oriented resultset elsewhere. A few other things to consider: - Cypher and/or Gremlin might provide ways to calculate individual facets via their aggregate functions. The only problem with this approach is that you'd probably need to make multiple traversals to calculate multiple unrelated facets. In "code" we can calculate those facets in a single pass - We use HashSets quite pervasively to keep lists of unique results that were the intersection of multiple "searches" and to manage collections of facets. The LinkedHashSet has been very helpful since it preserves the order with which items were added - Neo4J's index framework does not make it easy to (efficiently) get an exhaustive list of facet values/index values, if you're more interested in the key/value pairs and their frequency rather than the documents themselves I think it would be a nice feature to the Neo4J Lucene index implementation if we could have access to the IndexReader/IndexWriter with some specific caveats on what is "safe" to do. We contemplated hacking our own mods to the index framework to get access to this, but since we'd be missing the second part (the caveats), we felt like we'd just get into trouble. Hope this helps. Rick -----Original Message----- From: user-boun...@lists.neo4j.org [mailto:user-boun...@lists.neo4j.org] On Behalf Of Nils Kaiser Sent: Thursday, December 08, 2011 6:59 AM To: user@lists.neo4j.org Subject: [Neo4j] Facetted search in neo4j Hi, I'm new to neo4j and graph databases and currently experimenting with a video sharing application. One thing I don't see mention on the neo4j list a lot is facetted search. Is it because it is trivial to implement using graphs? I've used solr before, where I can return both search results and facet info (number of objects that would match that facet given the current search terms / facet choices) on a single call, so quite a luxury and really easy to implement. What would be the best approach with neo4j? I probably need to write a traversal that changes its stop conditions according to already entered search terms or facets, right? Anybody some examples or things to consider? Thanks, Nils -- Nils Kaiser MSc in Information Systems _______________________________________________ NOTICE: THIS MAILING LIST IS BEING SWITCHED TO GOOGLE GROUPS, please register and consider posting at https://groups.google.com/forum/#!forum/neo4j Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user _______________________________________________ NOTICE: THIS MAILING LIST IS BEING SWITCHED TO GOOGLE GROUPS, please register and consider posting at https://groups.google.com/forum/#!forum/neo4j Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
