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https://issues.apache.org/jira/browse/LUCENE-3068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13029150#comment-13029150
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Doron Cohen commented on LUCENE-3068:
-------------------------------------
This is more complex than I originally thought.
# QueryParser creates a MultiplePhraseQuery (MPQ) when one of the (phrase)
query positions is a multi-term.
# MPQ has an implicit OR behavior - it is used for e.g. wildcarding a phrase
query.
# PhraseQuery (PQ) sloppy scorer assumes each query position has a single term.
# PQ with several terms in same position cannot be created by parsing it with a
QP, only manual.
Manually created, it would have an AND semantics: only docs with ALL the
terms in pos N should match.
In other words, assume doc D terms and positions are:
a:0 b:1 c:1 d:2
MPQ for (a,b):0 d:1 should match D, finding the phrase b:1 d:2 (OR semantics)
PQ for (a,b):0 d:1 should not match D, because it does not contain 'a' and
'b' in the same position (AND semantics).
Therefore, rewriting PQ into MPQ is not a valid fix, because it would turn the
AND logic assumed by creating the PQ this way, by an OR logic as assumed in
MPQ.
{code:title=TestPositionIncrement.testSetPosition has a test for this case
exactly}
// phrase query should fail for non existing searched term
// even if there exist another searched terms in the same searched
position.
q = new PhraseQuery();
q.add(new Term("field", "3"),0);
q.add(new Term("field", "9"),0);
hits = searcher.search(q, null, 1000).scoreDocs;
assertEquals(0, hits.length);
{code}
Although QP by default will not create this PQ, I think we need to support it,
for applications needing to be strict with the search results, with slop.
So fixing this would need to take place inside SloppyScorer, digging further...
> The repeats mechanism in SloppyPhraseScorer is broken when doc has tokens at
> same position
> ------------------------------------------------------------------------------------------
>
> Key: LUCENE-3068
> URL: https://issues.apache.org/jira/browse/LUCENE-3068
> Project: Lucene - Java
> Issue Type: Bug
> Components: Search
> Affects Versions: 3.0.3, 3.1, 4.0
> Reporter: Michael McCandless
> Assignee: Doron Cohen
> Priority: Minor
> Fix For: 3.2, 4.0
>
> Attachments: LUCENE-3068.patch, LUCENE-3068.patch
>
>
> In LUCENE-736 we made fixes to SloppyPhraseScorer, because it was
> matching docs that it shouldn't; but I think those changes caused it
> to fail to match docs that it should, specifically when the doc itself
> has tokens at the same position.
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