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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Created] (LUCENE-4300) BooleanQuery inconsistently applies coord() if it rewrites itself
Date Thu, 09 Aug 2012 23:52:19 GMT
Robert Muir created LUCENE-4300:
-----------------------------------

             Summary: BooleanQuery inconsistently applies coord() if it rewrites itself
                 Key: LUCENE-4300
                 URL: https://issues.apache.org/jira/browse/LUCENE-4300
             Project: Lucene - Core
          Issue Type: Bug
            Reporter: Robert Muir


Tripped by the new random sim from LUCENE-4297:

The basics are this:
* BooleanQuery has the following rewrite():
{code}
  public Query rewrite(IndexReader reader) throws IOException {
    if (minNrShouldMatch == 0 && clauses.size() == 1) {                    // optimize
1-clause queries
{code}

* you have a coord() impl that doesnt return 1.0 if overlap == maxOverlap, particularly:
{code}
return overlap / ((float)maxOverlap + 1);
{code}

* TestBooleanMinShouldMatch.testRandomQueries generates random boolean queries (Q1), then
compares the scores of the random query to the same query but with minNrShouldmatch applied
to its should clauses (Q2)

* in the case of a single term BQ, the rewrite applies to Q1, making it a term query, but
not to Q2. so the coord() only gets called for Q2, not Q1. and with this crazy coord it means
the scores are different.

I think the rewrite is wrong, we should also rewrite single-query BQs where minNrShouldMatch
= 1 and there is a single optional clause.


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