[jira] [Created] (SOLR-15869) expand LTRRescorer.rescore test coverage

["Christine Poerschke (Jira)" <ji...@apache.org>]

Christine Poerschke created SOLR-15869:
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             Summary: expand LTRRescorer.rescore test coverage
                 Key: SOLR-15869
                 URL: https://issues.apache.org/jira/browse/SOLR-15869
             Project: Solr
          Issue Type: Test
          Components: contrib - LTR
            Reporter: Christine Poerschke
            Assignee: Christine Poerschke


On the dev mailing list https://lists.apache.org/thread/113d1yzty5ryvyt2o9msfytldv41qpgq thread [~4nn4r] shared about the discovery of the {{org.apache.solr.ltr.LTRRescorer#scoreSingleHit}} code block and how {{hitUpto >= topN}} never arises. I agree that the condition currently never evaluates to true due to how the rescore method is called:

* The Solr {{ReRankCollector}} caps the number of documents that are passed to the {{rescore}} method: https://github.com/apache/lucene-solr/blob/releases/lucene-solr/8.11.1/solr/core/src/java/org/apache/solr/search/ReRankCollector.java#L112-L119

* The Lucene {{Rescorer}} API however describes topN as the number of hits to return i.e. it is possible for firstPassTopDocs to contain more than topN documents: https://github.com/apache/lucene-solr/blob/releases/lucene-solr/8.11.1/lucene/core/src/java/org/apache/lucene/search/Rescorer.java#L51

This ticket here proposes to expand {{LTRRescorer.rescore}} test coverage to include the "more than topN documents are passed to be rescored" scenario.

(Whether or not the block of code in question could/should be removed I'd like to leave out of the scope of this current ticket here since on a high level not supporting {{topN != firstPassTopDocs.scoreDocs.length}} in {{LTRRescorer}} could simplify its code but on a practical level (at least theoretically) backwards compatibility would also need consideration and it's possible that some custom {{ReRankCollector}} (which we don't know of) does for some reason not cap the number of documents passed in the way {{ReRankCollector}} does.)



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