XSLT 3.0 partial streaming (Saxon)

Question

I have a big XML file (6 GB) with this kind of tree:

<Report>
   <Document>
      <documentType>E</documentType>
      <person>
         <firstname>John</firstname>
         <lastname>Smith</lastname>
      </person>
   </Document>
   <Document>
      [...]
   </Document>
   <Document>
      [...]
   </Document>
   [... there are a lot of Documents]
</Report>

So I used the new XSLT 3.0 streaming feature, with Saxon 9.6 EE. I don't want to have the streaming constrains once in a Document. This is why I tried to used copy-of(). I think that, what I want to do, is very close to the "burst mode" that is described here: http://saxonica.com/documentation/html/sourcedocs/streaming/burst-mode-streaming.html

Here is my XSLT style sheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3.0">
<xsl:mode streamable="yes" />

<xsl:template match="/">
    GLOBAL HEADER
        <xsl:for-each select="/Report/Document/copy-of()" >
           DOC HEADER
           documentType: <xsl:value-of select="documentType"/>
           person/firstname: <xsl:value-of select="person/firstname"/>

           <xsl:call-template name="fnc1"/>

           DOC FOOTER
        </xsl:for-each>
    GLOBAL FOOTER
</xsl:template>

<xsl:template name="fnc1">
    documentType again: <xsl:value-of select="documentType"/>
</xsl:template>

</xsl:stylesheet>

In a sense it works because with the copy-of() I'm able to use several xsl:value-of directly in the for-each (like in this question). (Otherwise I have this error * There are at least two consuming operands: {xsl:value-of} on line 8, and {xsl:value-of} on line 9)

But I still have streaming constrains because <xsl:call-template name="fnc1"/> creates this error:

Error at xsl:template on line 4 column 25 of stylesheet.xsl:
  XTSE3430: Template rule is declared streamable but it does not satisfy the streamability rules.
  * xsl:call-template is not streamable in this Saxon release
Stylesheet compilation failed: 1 error reported

So my question is: how to do partial streaming (Documents are loaded one by one but fully) in order to be able to use call-template (and other apply-templates) in a Document?

Thank you for your help!

Have you considered not to declare `` but instead to use `` and then you should be able to use any named and/or matching templates to processs `Document` element nodes and its descendants e.g. `DOC HEADER document type>...DOC FOOTER>`? — Martin Honnen, Oct 08 '14 at 14:26
I tried something with stream, but I had the same error. Now with your trick with `apply-templates` over a `copy-of()` it gives an error `Fatal error during transformation: java.lang.RuntimeException: Internal error evaluating template at line 4` — steco, Oct 08 '14 at 14:59

Michael Kay · Accepted Answer · 2014-10-08T19:36:10.100

1

I think call-template should be streamable when the context item is grounded (ie. not a streamed node), so I'll treat this as a bug. Meanwhile a workaround might be to declare fnc1 as

<xsl:template name="fnc1" mode="fnc1" match="Document"/>

and call it as

<xsl:apply-templates select="." mode="fnc1"/>

Alternatively, replace the template with a function and supply the context item as an explicit argument.

You can track the bug here:

https://saxonica.plan.io/issues/2171

Although we don't claim 100% conformance with the XSLT 3.0 specification yet, we'll treat any unnecessary departures in the 9.6 release as bugs unless fixing them would destabilize the product.

edited Oct 08 '14 at 19:36

answered Oct 08 '14 at 17:07

Michael Kay

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Thank you a lot, it is working well, good performance also (input 6.4GB, output 1.2GB, processing time 4 minutes). Just a little syntax error, we need the match attribute: ``. (I tried to edit your answer but I didn't know that people who don't know the topic can reject the edition, thanks to @tylerk @littlebobbytables @dmitry-fucintv ;) ) – steco Oct 08 '14 at 18:39
Thanks for the product feedback, xsl:call-template is now streamable in such cases. – Michael Kay Oct 08 '14 at 19:36

XSLT 3.0 partial streaming (Saxon)

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