[jira] [Created] (LUCENE-6255) PhraseQuery inconsistencies

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

Adrien Grand created LUCENE-6255:
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             Summary: PhraseQuery inconsistencies
                 Key: LUCENE-6255
                 URL: https://issues.apache.org/jira/browse/LUCENE-6255
             Project: Lucene - Core
          Issue Type: Bug
            Reporter: Adrien Grand
            Assignee: Adrien Grand


PhraseQuery behaves quite inconsistently when the position of the first term is greater than 0. Here is an example:

{noformat}
    Directory dir = newDirectory();
    RandomIndexWriter iw = new RandomIndexWriter(random(), dir);
    FieldType customType = new FieldType(TextField.TYPE_NOT_STORED);
    customType.setOmitNorms(true);
    Field f = new Field("body", "", customType);
    Document doc = new Document();
    doc.add(f);
    f.setStringValue("one quick fox");
    iw.addDocument(doc);
    IndexReader ir = iw.getReader();
    iw.close();
    IndexSearcher is = newSearcher(ir);
    
    PhraseQuery pq = new PhraseQuery();
    pq.add(new Term("body", "quick"), 0);
    pq.add(new Term("body", "fox"), 1);
    System.out.println(is.search(pq, 1).totalHits); // 1

    pq = new PhraseQuery();
    pq.add(new Term("body", "quick"), 10);
    pq.add(new Term("body", "fox"), 11);
    System.out.println(is.search(pq, 1).totalHits); // 0
    
    pq = new PhraseQuery();
    pq.add(new Term("body", "quick"), 10);
    System.out.println(is.search(pq, 1).totalHits); // 1
    
    pq = new PhraseQuery();
    pq.add(new Term("body", "quick"), 10);
    pq.add(new Term("body", "fox"), 11);
    pq.setSlop(1);
    System.out.println(is.search(pq, 1).totalHits); // 1
    
    ir.close();
    dir.close();
{noformat}

The reason is that when you add a term with position P on a PhraseQuery, ExactPhraseScorer ignores all positions for this term which are less than P.

But this is inconsistent:
 - if you have a single term, it does not work anymore since we rewrite to a term query regardless of the position of the term (3rd query)
 - if you increase the slop, we will use SloppyPhraseScorer which does not have this behaviour. (4th query)

So I think we have two options:
 - either remove this behaviour and make the positions that are provided to PhraseQuery only relative (ie. fix ExactPhraseScorer)
 - or make it work this way across the board (which means not rewriting to a term query when the position is not 0 and fixing SloppyPhraseScorer).



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