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https://issues.apache.org/jira/browse/XERCESJ-1276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16276496#comment-16276496
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Antti S. Lankila commented on XERCESJ-1276:
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Does a me-too help anything about finally resolving this bug report? I
discovered this same hot spot during slow XML validation using VisualVM on JDK
1.9 using the pure-java xerces parser (rather than the native C++ xerces
shipping in JDK, because all I could see that some native code was using all
the time). In my case, the pure-java Xerces was only slightly slower than the
C++ version, e.g. validating XML file took 1m50s using the native code, 2m5s
using the pure-Java version. However, with the Java code, I could replaces
xercesImpl with the one supplied on the 01/Feb/14 version, which dropped
runtime from 2m5s to just 5s. A significant improvement!
Incidentally libxml2 based validation was about as slow as Xerces, so I imagine
this library is also using linear scan for identity constraint validation. At
first, I thought it's just that schema validation is slow. However, I learnt
that .Net's XML validator was quite fast, doing the same work in about 10s,
which told me that there is a quality of implementation issue in Xerces.
> Improve performance of XML Schema Identity-constraint validation ---
> XMLSchemaValidator$ValueStoreBase.contains() is painfully slow.
> ------------------------------------------------------------------------------------------------------------------------------------
>
> Key: XERCESJ-1276
> URL: https://issues.apache.org/jira/browse/XERCESJ-1276
> Project: Xerces2-J
> Issue Type: Bug
> Components: XML Schema 1.0 Structures
> Affects Versions: 2.6.2, 2.9.1
> Reporter: Kenny MacLeod
> Labels: gsoc, gsoc2013, mentor
> Attachments: XMLSchemaValidator.java,
> Xerces-J-src.2.11.0_patch1276.txt, xerces-binaries-patched-over-2.11.0.zip,
> xerces-value-store.txt
>
>
> Under certain conditions, the contains() method in
> XMLSchemaValidator$ValueStoreBase can cripple the performance of parsing and
> validation.
> I'm not sure what those conditions are, but as a guideline figure I was using
> JAXB2 to deserialize a 22meg XML file. Without schema validation, it took 5
> seconds. With validation, it took over 3 minutes (JDK 1.5.0_10 on win32). My
> profiler pointed the finger squarely at that method XMLSchemaValidator.
> Suspicions were aroused further when seeing this comment in the source:
> public boolean contains() {
> // REVISIT: we can improve performance by using hash codes,
> instead of
> // traversing global vector that could be quite large.
> This is present in Xerces 2.6.2 contained with JDK1.5.0_10, and also in the
> source for 2.9.1.
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