[jira] [Created] (LUCENE-5307) Inconsistency between Weight.scorer documentation and ConstantScoreQuery on top of a Filter

["Adrien Grand (JIRA)" <ji...@apache.org>]

Adrien Grand created LUCENE-5307:
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             Summary: Inconsistency between Weight.scorer documentation and ConstantScoreQuery on top of a Filter
                 Key: LUCENE-5307
                 URL: https://issues.apache.org/jira/browse/LUCENE-5307
             Project: Lucene - Core
          Issue Type: Bug
            Reporter: Adrien Grand
            Assignee: Adrien Grand
            Priority: Minor


{{Weight.scorer}} states that if {{topScorer == true}}, {{Scorer.collect}} will be called and that otherwise {{Scorer.nextDoc/advance}} will be called.

This is a problem when {{ConstantScoreQuery}} is used on top of a {{QueryWrapperFilter}}:
 1. {{ConstantScoreWeight}}  calls {{getDocIdSet}} on the filter to know which documents to collect.
 2. {{QueryWrapperFilter.getDocIdSet}} returns a {{Scorer}} created with {{topScorer == false}} so that {{nextDoc/advance}} are supported.
 3. But then {{ConstantScorer.score(Collector)}} has the following optimization:
{code}
    // this optimization allows out of order scoring as top scorer!
    @Override
    public void score(Collector collector) throws IOException {
      if (docIdSetIterator instanceof Scorer) {
        ((Scorer) docIdSetIterator).score(wrapCollector(collector));
      } else {
        super.score(collector);
      }
    }
{code}

So the filter iterator is a scorer which was created with {{topScorer = false}} but {{ParentScorer}} ends up using its {{score(Collector)}} method, which is illegal. (I found this out because AssertingSearcher has some checks to make sure Scorers are used accordingly to the value of topScorer.)

I can imagine several fixes, including:
 - removing this optimization when working on top of a filter
 - relaxing Weight documentation to allow for using {{score(Collector)}} when {{topScorer == false}}

but I'm not sure which one is the best one. What do you think?



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