XSLT streaming not streaming - streaming

Question

I'm using Saxon-EE for the purpose of streaming XSLT transformation of large XML. The transformation works fine but it seems it's not really streaming since the java.exe process is inflating: for a 100 MB XML, process memory increases ~1GB. This is the XSLT:
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:fo="http://www.w3.org/1999/XSL/Format"
xmlns:bb="urn:xx-zz-1.1"
xmlns:aa="urn:xx-yy-1.1">
<xsl:mode streamable="yes"/>
<xsl:output method="text" omit-xml-declaration="yes" indent="no"/>
<xsl:template match="/">
<xsl:for-each select="aa:LevelOne/aa:LevelTwo">
<xsl:iterate select="bb:LevelThree! copy-of(.)">
<xsl:value-of select="concat(bb:fieldOne,',',bb:fieldTwo,'
')"/>
</xsl:iterate>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
This is the XML:
<?xml version="1.0" encoding="utf-8"?>
<aa:LevelOne xmlns="urn:xx-zz-1.1" xmlns:aa="urn:xx-yy-1.1">
<aa:LevelTwo xmlns="urn:xx-zz-1.1" xmlns:aa="urn:xx-yy-1.1">
<LevelThree xmlns="urn:xx-zz-1.1">
<fieldOne>f1</fieldOne>
<fieldTwo>f2</fieldTwo>
</LevelThree>
<!-- Level three is repeated many times -->
</aa:LevelTwo>
</aa:LevelOne>
I would like to know if there (& what) is a problem with the XSLT above.
The code I use:
net.sf.saxon.s9api.Processor processor = new net.sf.saxon.s9api.Processor(true);
processor.setConfigurationProperty(Feature.STREAMABILITY, "standard");
XsltCompiler compiler = processor.newXsltCompiler();
XsltExecutable stylesheet = compiler.compile(new StreamSource(stylesheetFile));
Serializer out = processor.newSerializer(outputCsvFile);
Xslt30Transformer transformer = stylesheet.load30();
transformer.applyTemplates(new StreamSource(xmlFile), out);
EDIT: Fixed the XSLT so it compiles & added XML example.
Remark: using command java -cp "<path>\test;<path>\saxon9ee.jar" com.example.test.Test -t does not ouput additional info (only the printlns in the code). java -cp "<path>\test;<path>\saxon9ee.jar" -t com.example.test.Test outputs: Unrecognized option: -Xt Error: Could not create the Java Virtual Machine. If I change the XSLT to non-streamable rule e.g. remove the iterate line, program outputs Template rule is not streamable, also without -t option. In this case if I remove the streamability requirement from code/xslt, the error goes away.
Thanks.

Answer 1

Probably the most likely reason Saxon would fall back to non-streaming mode is that it hasn't located a Saxon-EE license. The easiest way to test that is (unintuitively!) by calling processor.isSchemaAware() - that will only be true if you're running Saxon-EE code with a recognized license, which is exactly the same condition to enable streaming.
If it hasn't found a license, the Saxon documentation includes a section on troubleshooting license problems at http://www.saxonica.com/documentation/index.html#!about/license
Also, try it from the command line with option -t; that will give you more information (a) about streaming, and (b) about loading of license files.

Answer 2

I think, if the data is as simple and as regular as shown in the question, then you can avoid the use of copy-of() and simply use
<xsl:iterate select="bb:LevelThree">
<xsl:value-of select="bb:*" separator=","/>
<xsl:text>
</xsl:text>
</xsl:iterate>
That in a quick test shows a reduced memory consumption compared to your posted approach.
As for your posted approach not using streaming with Saxon EE 9.9, I have tested the posted XSLT and the input sample with Saxon 9.9 EE from the command line with the -t option and it shows the input is streamed.
I also think the Java code shown is fine to process the file with streaming with Saxon EE.
For a detailed analysis of the memory consumption and any problems you encounter with that it might be better to raise an issue with all details on the Saxonica support site. I am not sure how the memory info Saxon outputs relates exactly to the one you say you see for java.exe.