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https://issues.apache.org/jira/browse/LUCENE-6255?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand updated LUCENE-6255:
---------------------------------
Attachment: LUCENE-6255.patch
Here is a middle ground proposal:
- enforce that terms are added in order of positions
- enforce that positions are all positive
- PhraseQuery still accepts that the first position is greater than 0 but
PhraseWeight does not
- PhraseQuery.rewrite takes care of rebasing positions if the first one is not 0
This way, PhraseQuery would still be friendly to query parsers that create
phrase queries from a token stream.
> 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
> Attachments: LUCENE-6255.patch
>
>
> 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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