Hi all.

to close my thread:

My requirement was to build a simple scoring system that basically reuses Lucene's index infrastructure but not its advanced scoring system, i.e., I had to replace the query and scorer infrastructure with my own implementation.

In detail I had to come up with my own versions of:
The usage of this API looks similar to standard Lucene usage:

ExamplesSearchQuery query = LuceneQueryUtil.toCodeSearchQuery(request);
IndexSearcher searcher = new IndexSearcher(luceneIndexReader);
TopDocs search = searcher.search(query, 15);

To accomplish my scoring function, the scorer delegates to several subscorers similar to the BooleanScorer and sums up the sub-scores to build the final score.

Since yesterday, the first prototype based on Lucene is available for download and a blog-post showing the Eclipse integration in action is available here:
http://code-recommenders.blogspot.com/2010/07/why-is-google-codesearch-not-google-for.html - and I would be glad to take your comments on the post :-)

Thanks again for your help on Lucene,

On 11.06.2010 18:12, wrote Marcel Bruch:
Sounds like an interesting project.
I think it is :-) It's tightly integrated into Eclipse where (i) it grabs your code of your current editor on demand, (ii) automatically creates and submits a query from it, and (iii) displays the best code examples directly aside your editor in a separate view. As soon as scoring works with Lucene you can test the first version in a week or two.

However, can I implement this scoring function with Lucene:
score(d,q) = \sum_{i \in I} w_i * f_i(d,q)