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Subject: XOM API for Processing XML with Java

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  • From: Wolfgang Hoschek <whoschek AT lbl.gov>
  • To: shirasu hiroyuki <hirsh AT s9.dion.ne.jp>
  • Cc: xom-interest AT lists.ibiblio.org
  • Subject: Re: [XOM-interest] Performance of Java XPath engines
  • Date: Wed, 19 Jan 2005 17:47:20 -0800

On Jan 19, 2005, at 5:05 PM, shirasu hiroyuki wrote:

Dear Elliote, Michael and Wolfgang,

Thank you very much for your valuable comments. I learn
a lot things from them. I must apologize for the delay
in replying and for my poor English. I write English very
slowly.

You are most welcome and your work is appreciated very much!


I know that performance of Saxon for precompiled expressions
is better than ones of the other engines.
I planed to check performance of XPath engines for pre-
compiled XPath expressions first. But I does not understand
how engines process lifecycle and size of cache for pre-
compiled expressions.

You can manage those any way you like. The simplest way is to keep the compiled query around in your own variables. Or you can use a slightly more elaborate cache, typically via some hashmap. One such straightforward cache has its lifecycle, thread-safety and management options documented at http://dsd.lbl.gov/nux/api/nux/xom/pool/XQueryPool.html. A plethora of similar schemes could be used, perhaps more elaborate in its eviction strategy. But a cache can be made very effectively - I'd be surprised if it should turn out to be counter productive in practise...

To evaluate precompiled expressions
simply multi times may cause worse performance than non
precompiled case sometimes (especially, JXPath).
I would like to study a lot and improve my observation.

Thanks,
--
shirasu hiroyuki(hirsh AT s9.dion.ne.jp)
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