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Posted to users@jackrabbit.apache.org by Oliver Wehrens <we...@aei.mpg.de> on 2006/04/07 16:45:49 UTC

Xpath question

Hi,

I have some trouble with xpath queries to jackrabbit.

I want to select the 5th entry and my query would look something like:

q = qm.createQuery("//wiki:entry[5]", Query.XPATH);
qr = q.execute();
NodeIterator it = qr.getNodes();
while (it.hasNext()) {
   Node n = it.nextNode();
System.out.println("n.getProperty("wiki:content").getValue().getString());
}

But if I get back the NodeIterator it contains all nodes...where does it go
wrong ?

Variations with //wiki:entry[position()=last()] or things like that also
always give me back the whole list ?

What I try to achieve at the end is to get back the sorted ten last entries
by time (so a order by a property and position()<10, e.g.
//wiki:entry[position()<10] order by @wiki:date descending).

Is that possible (well I guess so but I just don't know how).

Does anybody has an idea?

Thanks, Oliver



-- 
Oliver Wehrens
+49 170 785 1323
http://wehrens.net/oliver

Re: Xpath question

Posted by Oliver Wehrens <we...@aei.mpg.de>.
Hi,

I just checked it with the latest svn version and it still does not work how
I think it should. I will submit a bug report.


On 10.04.2006 10:52 Uhr, "Marcel Reutegger" <ma...@gmx.net>
wrote:

> Hi Oliver,
> 
> Oliver Wehrens wrote:
>> I have some trouble with xpath queries to jackrabbit.
>> 
>> I want to select the 5th entry and my query would look something like:
>> 
>> q = qm.createQuery("//wiki:entry[5]", Query.XPATH);
>> qr = q.execute();
>> NodeIterator it = qr.getNodes();
>> while (it.hasNext()) {
>>    Node n = it.nextNode();
>> System.out.println("n.getProperty("wiki:content").getValue().getString());
>> }
>> 
>> But if I get back the NodeIterator it contains all nodes...where does it go
>> wrong ?
> 
> this is a bug in the query builder. could you please create a jira
> issue? Thanks.
> 
> the problem is with the descendant-or-self axis. if you just use the
> child node axis queries with position predicates work. e.g. something
> like this:
> 
> /jcr:root/*/wiki:entry[5]
> 
>> Variations with //wiki:entry[position()=last()] or things like that also
>> always give me back the whole list ?
> 
> same bug as above.
> 
>> What I try to achieve at the end is to get back the sorted ten last entries
>> by time (so a order by a property and position()<10, e.g.
>> //wiki:entry[position()<10] order by @wiki:date descending).
> 
> this is actually not yet supported in jackrabbit. so far you can only
> use position predicates with the equals operator.
> 
> I'm not sure I understand your use case. If it were possible to execute
> the previous query in jackrabbit you would get the *first* ten
> wiki:entry nodes (in document order) and then sorted by date. I guess
> what you rather want are the 10 latest wiki entries, right?
> 

Jupp, make it ascending it the query above ;)

Thanks, Oliver

> regards
>   marcel
> 

-- 
Oliver Wehrens
+49 170 785 1323
http://wehrens.net/oliver

Re: Xpath question

Posted by Marcel Reutegger <ma...@gmx.net>.
Hi Oliver,

Oliver Wehrens wrote:
> I have some trouble with xpath queries to jackrabbit.
> 
> I want to select the 5th entry and my query would look something like:
> 
> q = qm.createQuery("//wiki:entry[5]", Query.XPATH);
> qr = q.execute();
> NodeIterator it = qr.getNodes();
> while (it.hasNext()) {
>    Node n = it.nextNode();
> System.out.println("n.getProperty("wiki:content").getValue().getString());
> }
> 
> But if I get back the NodeIterator it contains all nodes...where does it go
> wrong ?

this is a bug in the query builder. could you please create a jira
issue? Thanks.

the problem is with the descendant-or-self axis. if you just use the
child node axis queries with position predicates work. e.g. something
like this:

/jcr:root/*/wiki:entry[5]

> Variations with //wiki:entry[position()=last()] or things like that also
> always give me back the whole list ?

same bug as above.

> What I try to achieve at the end is to get back the sorted ten last entries
> by time (so a order by a property and position()<10, e.g.
> //wiki:entry[position()<10] order by @wiki:date descending).

this is actually not yet supported in jackrabbit. so far you can only
use position predicates with the equals operator.

I'm not sure I understand your use case. If it were possible to execute 
the previous query in jackrabbit you would get the *first* ten 
wiki:entry nodes (in document order) and then sorted by date. I guess 
what you rather want are the 10 latest wiki entries, right?

regards
  marcel