Saxon

On 18 Oct 2014, at 10:23, Costello, Roger L. costello@mitre.org wrote [on the saxon-help list]:

Hi Michael,

The below program generates a huge amount of output, using streaming.

It worked fine in Saxon version 9.5.1.6

It fails in the latest version of Saxon - an Out of Memory error is generated.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

           xmlns:math="http://www.w3.org/2005/xpath-functions/math"

           version="3.0">

<xsl:output method="xml" />

<xsl:mode streamable="yes" />

<xsl:template match="/">

   <sine-values>

       <xsl:for-each select="0 to 100000000">

           <sine>

               <number><xsl:value-of select="." /></number>

               <sine><xsl:value-of select="math:sin(.)" /></sine>

           </sine>

       </xsl:for-each>

   </sine-values>

</xsl:template>

</xsl:stylesheet>

My response:

Interesting!

Firstly, "streaming" in the XSLT 3.0 sense is all about streaming the input; the spec takes for granted that streaming the output isn't a problem. But here, the problem is that the output isn't being streamed.

What seems to be happening here is that when you execute a non-consuming template in streaming mode then it is evaluated in "pull" rather than "push" mode, which means any output from that template rule is built in memory rather than being streamed straight to the result stream. Your match="/" is non-consuming (it doesn't read anything from the input document), and it's executed in streaming mode (because the mode is declared streamable), so the element is being constructed in memory. I don't think there is any particularly good reason for this.

Michael Kay

Saxonica

The issue is at ApplyTemplatesAction line 233 where we do:

            SequenceIterator si = body.iterate(localContext);

            processItems(si, out);

Executing the body using iterate() rather than process() in this case causes the single element produced by the template to be materialized, and then written to the output in a single call of processItems.