It's a Java object. Solr actually replaces it with a different
implementation called OpenBitSet:
http://lucene.apache.org/solr/api/org/apache/solr/util/OpenBitSet.html ,
for performance. Solr's use of them in managing facets is discussed in
the wiki: http://wiki.apache.org/solr/SimpleFacetParameters , in the
description of FacetQueries .

Peter

-----Original Message-----
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of
Alan Darnell
Sent: Friday, January 19, 2007 1:03 PM
To: [log in to unmask]
Subject: Re: [CODE4LIB] Limiting by availability (was Re: [CODE4LIB]
Getting data from Voyager into XML?)

Peter,

What is a bitset?  Is it a Java class or a more primitive data
structure?

Alan


On 19-Jan-07, at 2:32 PM, Binkley, Peter wrote:

> This is why I think we should figure out smart ways to manage facets
> independently of Lucene index fields. Solr populates a facet by
> setting up a bitset for every value found in a given index field, and
> it uses those bitsets to filter query result sets by deriving an
> intersection set. We can extend that functionality by populating and
> maintaining bitsets based on external data sources that can map to
> Lucene document ids. This allows us to update the bitset (relatively
> cheap) without having to update the index (relatively expensive).