Hi guys: We have build this on top of the lucene 1.4. api/refactoring for docid sets and docIdIterater.
We've implemented the p4Delta compression algorithm presented at www2008: http://www2008.org/papers/fp618.html We've been using this in production here at LinkedIn and would love to contribute it into lucene. We currently open sourced it at: http://code.google.com/p/lucene-ext/wiki/Kamikaze Please let us know if it is thing you guys want to proceed, if so, what are the steps we should take. Thanks -John