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Date: Sun, 6 Jun 2010 04:16:55 -0400 (EDT)
From: "Waruna Ranasinghe (JIRA)" <jira@apache.org>
To: dev@openjpa.apache.org
Subject: [jira] Created: (OPENJPA-1684) Prepared query cache won't work if
 the start index (i.e setFirstResult) is changed
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Prepared query cache won't work if the start index (i.e setFirstResult) is changed
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                 Key: OPENJPA-1684
                 URL: https://issues.apache.org/jira/browse/OPENJPA-1684
             Project: OpenJPA
          Issue Type: Bug
          Components: query
    Affects Versions: 2.0.0
         Environment: Ubuntu 9.04, Sun jdk6, database: H2 
            Reporter: Waruna Ranasinghe


I have implemented pagination so that only 6 entries are fetched for a page.
First, I get the first 6 entries (First page: from 0 to 6) by setting ;
    query = query.setFirstResult(startIndex); //startindex = 0
    query = query.setMaxResults(pageSize); //pageSize = 6

Then the db query is sent as follow: 
    SELECT t0.id FROM ....... LIMIT ?
And the above sql is cached against its JPQL

When I try to get the next page (Second page: from 6 to 12) by setting;
    query = query.setFirstResult(startIndex); //startindex = 6
    query = query.setMaxResults(pageSize); //pageSize = 6

Then the db query is still sent as follow: 
    SELECT t0.id FROM ....... LIMIT ?
Where as it should be 
      SELECT t0.id FROM ....... LIMIT ? OFFSET ?

This problem occurs because it takes the SQL query from the cache against the JPQL (JPQL is same as the first) which returns the old SQL query in which there was no any OFFSET keyword set.

This can be fixed by setting the OFFSET value (in H2) to zero even if it is the default value OR setting the relevant keyword (OFFSET in H2, LIMIT in MySQL) to default, so that it can be taken from the cache and the changed offset values will be set without a problem.


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