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From "Marcel Reutegger (JIRA)" <j...@apache.org>
Subject [jira] Created: (JCR-2759) Collapse nested OR expressions
Date Tue, 28 Sep 2010 08:27:32 GMT
Collapse nested OR expressions

                 Key: JCR-2759
                 URL: https://issues.apache.org/jira/browse/JCR-2759
             Project: Jackrabbit Content Repository
          Issue Type: Improvement
          Components: jackrabbit-core
            Reporter: Marcel Reutegger
            Priority: Minor

Executing a query with multiple OR expressions in a predicate leads to score values that depend
on the order of the operands.

For example, the following query:

//*[jcr:contains(@prop1, 'foo') or jcr:contains(@prop2, 'foo') or jcr:contains(@prop3, 'foo')]
order by @jcr:score descending

will return a slightly different result compared to:

//*[jcr:contains(@prop3, 'foo') or jcr:contains(@prop1, 'foo') or jcr:contains(@prop2, 'foo')]
order by @jcr:score descending

Internally jackrabbit parses the predicate of the first query into a tree:

orExpr(orExpr(contains(prop1, 'foo'), contains(prop2, 'foo')), contains(prop3, 'foo'))

Lucene will calculate the score for the inner OR expression first and then for the outer,
which is not equivalent with a nested expression that has property names in a different sequence.

The query should be translated internally into a single OR expression with three operands.
That way, the score value is always the same, irrespective of the order of the operands.

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