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Posted to dev@tomcat.apache.org by Jeremy Boynes <jb...@apache.org> on 2010/10/02 20:08:31 UTC
Re: [taglibs] XPath support
On Jul 15, 2010, at 12:19 AM, Henri Yandell wrote:
> On Wed, Jul 14, 2010 at 8:45 PM, Jeremy Boynes <jb...@apache.org> wrote:
>> On Jul 12, 2010, at 7:04 PM, Jeremy Boynes wrote:
>>
>>> I'm going to ping Xalan about the increase in time taken as expressions are evaluated as I would assume I'm doing something silly.
>>
>> I looked into the Xalan implementation and the problem appears to be in creation of the DTM used by the underlying implementation. To evaluate the expression it walks up the DOM tree to the parent and then iterates forward over the tree until it reaches the initial context node. This leads to a linear increase in execution time as the context node progresses through the NodeList from the <forEach>.
>>
>> I changed <x:forEach> and <x:out> to use Jaxen and did not see this issue. The execution time for xpath evalutation over 1000 iterations was constant and substantially faster than with Xalan: total of 62ms reparsing each time or 21ms if precompiled, down from 1800ms.
>>
>> In light of this I'd like to propose we switch to Jaxen and add it as a dependency.
>
> Absolutely: +1
>
> Great work :)
I've not committed these changes as the latest version of Jaxen is not available in the Maven repo and there did not appear to be much interest in doing so. We might be able to get similar improvements using JXPath.
--
Jeremy
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Re: [taglibs] XPath support
Posted by Rex Wang <rw...@gmail.com>.
2010/10/3 Jeremy Boynes <jb...@apache.org>
> On Jul 15, 2010, at 12:19 AM, Henri Yandell wrote:
>
> > On Wed, Jul 14, 2010 at 8:45 PM, Jeremy Boynes <jb...@apache.org>
> wrote:
> >> On Jul 12, 2010, at 7:04 PM, Jeremy Boynes wrote:
> >>
> >>> I'm going to ping Xalan about the increase in time taken as expressions
> are evaluated as I would assume I'm doing something silly.
> >>
> >> I looked into the Xalan implementation and the problem appears to be in
> creation of the DTM used by the underlying implementation. To evaluate the
> expression it walks up the DOM tree to the parent and then iterates forward
> over the tree until it reaches the initial context node. This leads to a
> linear increase in execution time as the context node progresses through the
> NodeList from the <forEach>.
> >>
> >> I changed <x:forEach> and <x:out> to use Jaxen and did not see this
> issue. The execution time for xpath evalutation over 1000 iterations was
> constant and substantially faster than with Xalan: total of 62ms reparsing
> each time or 21ms if precompiled, down from 1800ms.
> >>
> >> In light of this I'd like to propose we switch to Jaxen and add it as a
> dependency.
> >
> > Absolutely: +1
> >
> > Great work :)
>
> I've not committed these changes as the latest version of Jaxen is not
> available in the Maven repo and there did not appear to be much interest in
> doing so. We might be able to get similar improvements using JXPath.
>
>
Could we start the release process without resolving this performance issue?
If not, the servicemix bundled jaxen
http://repo1.maven.org/maven2/org/apache/servicemix/bundles/org.apache.servicemix.bundles.jaxen/1.1.1_1/
might be a good choice as the dependency.
-Rex
> --
> Jeremy
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>
--
Lei Wang (Rex)
rwonly AT apache.org