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Subject: XOM API for Processing XML with Java

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  • From: Michael Kay <mike AT saxonica.com>
  • To: xom-interest AT lists.ibiblio.org
  • Subject: Re: [XOM-interest] Processing XML file of 4GB
  • Date: Mon, 30 Apr 2012 13:11:21 +0100

NUX implements what one might call "chunked streaming": it selects a sequence of subtrees of your document and applies XQuery processing to each one in turn. (This is effectively the same as saxon:stream() in Saxon.) You need to have enough memory to hold the largest of these subtrees. Because your path /xbrli:xbrl effectively selects the whole document, your largest subtree is the same as the document size, so you aren't really streaming at all.

If you can describe the query/transformation you want to carry out, then I might be able to suggest a way of doing it in a streamed manner either using NUX, or using native facilities of Saxon (whose streaming capabilities have advanced considerably since NUX was last released).

Michael Kay
Saxonica


2012/4/30 Geet Gangwar <geetgangwar AT gmail.com>
Hi,

I have a requirement of processing large XML files of about 4GB. I am using
the NUX distribution to process the files.
But when I fire a Xquery to this read this file, I get JAVA Heap Space
error.

I am using 64bit JDK1.6 and also I have increased the JVM size to 5 GB by
-Xmx5G.

Please help me how to solve this problem.

I am pasting my sample code also.

String path = "/xbrli:xbrl/";
Map prefixes = new HashMap();
prefixes.put("xbrli", "http://www.xbrl.org/2003/instance";);
prefixes.put("link", "http://www.xbrl.org/2003/linkbase";);
prefixes.put("xlink", "http://www.w3.org/1999/xlink";);
prefixes.put("xsd", "http://www.w3.org/2001/XMLSchema";);

StreamingTransform myTransform = new StreamingTransform() {
private Nodes NONE = new Nodes();

// execute XQuery against each element matching location
path
public Nodes transform(Element subtree) {
Nodes results = XQueryUtil.xquery(subtree,
"xbrli:context[id = 'c-01']");

for (int i=0; i< results.size(); i++) {
// do something useful with query results; here we
just print them

System.out.println(XOMUtil.toPrettyXML(results.get(i)));
}
return NONE; // current subtree becomes subject to
garbage collection
// returning empty node list removes current subtree
from document being build.
// returning new Nodes(subtree) retains the current
subtree.
// returning new Nodes(some other nodes) replaces the
current subtree with
// some other nodes.
// if you want (SAX) parsing to terminate at this
point, simply throw an exception
}
};

// parse document with a filtering Builder
StreamingPathFilter filter = new StreamingPathFilter(path,
prefixes);
Builder builder = new Builder(filter.createNodeFactory(null,
myTransform));
Document doc = builder.build(new File("F:/sample/cntxt.xml"));
System.out.println(doc.getRootElement().getValue());
System.out.println("doc.size()=" +
doc.getRootElement().getChildCount());
System.out.println(XOMUtil.toPrettyXML(doc));

Regards

Geet
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