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From "Julian Reschke (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (JCR-3261) Problems with BundleDbPersistenceManager getAllNodeIds
Date Mon, 19 Mar 2012 09:53:37 GMT

    [ https://issues.apache.org/jira/browse/JCR-3261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13232529#comment-13232529
] 

Julian Reschke commented on JCR-3261:
-------------------------------------

> What is your use case, that is, why do you need getAllNodeIds? I'm just wondering if
we really need this method... If we could remove it then we wouldn't have to deal with such
problems. 

It's needed by the datastore garbage collector and the consistency checker.
                
> Problems with BundleDbPersistenceManager getAllNodeIds
> ------------------------------------------------------
>
>                 Key: JCR-3261
>                 URL: https://issues.apache.org/jira/browse/JCR-3261
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>    Affects Versions: 2.4
>            Reporter: Unico Hommes
>             Fix For: 2.4.1
>
>         Attachments: bdbpm_allids.patch
>
>
> When using MySQL:
> The problem arises when the method parameter maxcount is less than the total amount of
records in the bundle table.
> First of all I found out that mysql orders the nodeid objects different than jackrabbit
does. The following test describes this idea:
>     public void testMySQLOrderByNodeId() throws Exception {
>         NodeId nodeId1 = new NodeId("7ff9e87c-f87f-4d35-9d61-2e298e56ac37");
>         NodeId nodeId2 = new NodeId("9fd0d452-b5d0-426b-8a0f-bef830ba0495");
>         PreparedStatement stmt = connection.prepareStatement("SELECT NODE_ID FROM DEFAULT_BUNDLE
WHERE NODE_ID = ? OR NODE_ID = ? ORDER BY NODE_ID");
>         Object[] params = new Object[] { nodeId1.getRawBytes(), nodeId2.getRawBytes()
};
>         stmt.setObject(1, params[0]);
>         stmt.setObject(2, params[1]);
>         ArrayList<NodeId> nodeIds = new ArrayList<NodeId>();
>         ResultSet resultSet = stmt.executeQuery();
>         while(resultSet.next()) {
>             NodeId nodeId = new NodeId(resultSet.getBytes(1));
>             System.out.println(nodeId);
>             nodeIds.add(nodeId);
>         }
>         Collections.sort(nodeIds);
>         for (NodeId nodeId : nodeIds) {
>             System.out.println(nodeId);
>         }
>     }
> Which results in the following output:
> 7ff9e87c-f87f-4d35-9d61-2e298e56ac37
> 9fd0d452-b5d0-426b-8a0f-bef830ba0495
> 9fd0d452-b5d0-426b-8a0f-bef830ba0495
> 7ff9e87c-f87f-4d35-9d61-2e298e56ac37
> Now the problem with the getAllNodeIds method is that it fetches an extra 10 records
on top of maxcount (to avoid a problem where the first key is not the one you that is wanted).
Afterwards it skips a number of records again, this time using nodeid.compareto. This compareto
statement returns true unexpectedly for mysql because the code doesn't expect the mysql ordering.
> I had the situation where I had about 17000 records in the bundle table but consecutively
getting the ids a thousand records at a time returned only about 8000 records in all.

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