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From "bernard (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-1553) JPQL simple Child query generates unnecessary Table Join
Date Sun, 07 Mar 2010 20:16:27 GMT
JPQL simple Child query generates unnecessary Table Join
--------------------------------------------------------

                 Key: OPENJPA-1553
                 URL: https://issues.apache.org/jira/browse/OPENJPA-1553
             Project: OpenJPA
          Issue Type: Bug
          Components: jpa
    Affects Versions: 2.0.0-beta2
         Environment: Java 6
            Reporter: bernard


The attached testcase demonstrates that for a basic child query, OpenJPA generates SQL that
contains two joined tables where only one is required.

SELECT t0.id, t1.id FROM Child t0 LEFT OUTER JOIN Parent t1 ON t0.PARENT_ID = t1.id WHERE
(t0.PARENT_ID = ?)

This creates performance issues. Please note that this is a simplified testcase - performance
issues are of course not present in it.

It can be expected that JPA that provides a layer of abstraction by nature, generates optimized
SQL.

In light of the fact that this is a 2.0 release, the priority of solving this should be high.



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