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From "Marcel Reutegger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-2302) Child axis support in order by clause does not work
Date Fri, 11 Sep 2009 08:07:57 GMT

    [ https://issues.apache.org/jira/browse/JCR-2302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12754038#action_12754038

Marcel Reutegger commented on JCR-2302:

> It would be useful if it always follows the same order in that case (also for multiple
executions of the same query), so that components that 
> automatically show you the latest content by running a query every 20 seconds or so have
a stable result. 

IIRC the result is stable in jackrabbit, it just may be different depending on how ordering
is calculated. 

A little bit of background info: there are two implementations responsible for result ordering:

- RelPathScoreDocComparator, this one is generally used when you have an order by with a relative
- SimpleScoreDocComparator, this one is generally used when you have an order by on a property
of a result node 

there's one exception though, when you define an index aggregate with a include-property that
matches the relative path of your order by, then the SimpleScoreDocComparator is used. 

I think it is be up to the application if it want to put additional ordering on the result
set. Either by applying that ordering manually after the query execution or by specifying
a secondary order property.

> Child axis support in order by clause does not work
> ---------------------------------------------------
>                 Key: JCR-2302
>                 URL: https://issues.apache.org/jira/browse/JCR-2302
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: jackrabbit-core, jackrabbit-spi-commons, xpath
>    Affects Versions: 2.0-alpha9
>            Reporter: Alexander Klimetschek
>            Priority: Minor
> Child axis support for order by in xpath queries was introduced with JCR-800.
> In my use case I have a cq:Page nodetype which has a jcr:content child of type cq:PageContent
(like nt:file and nt:resource). The jcr:content child has a cq:lastModified time stamp that
I want to search on. I use descending to see the most recently modified nodes at the top.
> The problem is that it does not work when using a child axis in the order by:
> (1) //element(*, cq:Page) order by @jcr:content/cq:lastModified descending
> This gives a different (and wrong) result compared to the simpler query on level deeper,
which returns the correct results:
> (2) //element(*, cq:PageContent) order by @cq:lastModified descending
> Switching between ascending and descending in (1) does not change the result set at all,
ie. the order stays the same.
> A reason could be non-existing properties (of which there are some in my data), so to
only look at existing properties, I run this query, which still gives incorrect results:
> (3) //element(*, cq:Page)[jcr:content/@cq:lastModified] order by @jcr:content/cq:lastModified

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