Michael Kay wrote:
In Saxon, and I suspect in most processors, no memory is used for the
result tree provided that the transformation is writing directly to a
serializer.
So if I use xsl:copy and the results of the copy are immediately output, then
there is little or no memory consumption. Yes?
However, in my situation I need to store the results of xsl:copy into a
variable. Then I process the variable. That processing also uses xsl:copy. I
put those results into another variable. And again and again.
So in my situation is xsl:copy consuming lots of memory?
In other words, if I don't immediately output the results of xsl:copy, then
memory consumption grows and grows. Yes?
/Roger
-----Original Message-----
From: Michael Kay [mailto:mike(_at_)saxonica(_dot_)com]
Sent: Sunday, September 02, 2012 10:31 AM
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: Re: [xsl] Does <xsl:copy> use a lot of memory? Is there an alternative
that is more efficient?
Memory is used for the source document and for intermediate variables.
In Saxon, and I suspect in most processors, no memory is used for the
result tree provided that the transformation is writing directly to a
serializer.
Intrinsically, all xsl:copy has to do is to send two events -
startElement and endElement - to the serializer.
I would strongly suspect that the out of memory error occurs during
building of the source tree, and will happen whatever transformation
you run. For a 370Mb input document, you should probably allocate at
least 2Gb of memory, preferably more.
Michael Kay
Saxonica
On 02/09/2012 13:47, Costello, Roger L. wrote:
Hi Folks,
Does <xsl:copy> use a lot of memory?
Is there an alternative that is more efficient?
Consider this problem. I have an XML document in which some elements have an
id attribute and others have an idref attribute. If an element A references
element B, then I want to embed B inside A.
Example: I want to convert this:
<Test>
<A idref="b" />
<B id="b" />
</Test>
to this:
<Test>
<A>
<B id="b" />
</A>
<B id="b" />
</Test>
Notice that A references B, and after processing B is nested inside A.
Here's a template that handles elements with a reference:
<xsl:key name="ids" match="*[@id]" use="@id"/>
<xsl:template match="*[@idref]">
<xsl:variable name="refed-element" select="key('ids', @idref)"/>
<xsl:copy>
<xsl:copy-of select="@* except @idref" />
<xsl:sequence select="$refed-element" />
</xsl:copy>
</xsl:template>
The complete program is below.
It works fine if:
(a) The XML document is small.
(b) I don't have to repeat this embedding process too many times.
However, such is not the case. I am dealing with an XML document that is 370
MB in size and has tens of thousands of references. And I have to repeat the
embedding process multiple times.
Saxon gives me an "out of memory error."
I suspect the reason for this is due to the <xsl:copy> command. I believe it
is making new copies, thereby consuming lots of memory. True?
So, is there an alternative to <xsl:copy> that is more efficient?
Is there a way to express the above template rule that is more efficient?
/Roger
-----------------------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
exclude-result-prefixes="#all"
version="2.0">
<xsl:output method="xml" />
<xsl:key name="ids" match="*[@id]" use="@id"/>
<xsl:template match="*[@idref]">
<xsl:variable name="refed-element" select="key('ids', @idref)"/>
<xsl:copy>
<xsl:copy-of select="@* except @idref" />
<xsl:sequence select="$refed-element" />
</xsl:copy>
</xsl:template>
<xsl:template match="node()">
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:apply-templates />
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
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