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[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Comparing grouping techniques in terms of performance
 Hi all,
looking at various requests in the list regarding grouping, especially the
Muenchian Method, explained very well by Jeni at
http://www.jenitennison.com/xslt/grouping/muenchian.html, and another
method I regularly have seen before, that uses
template processing rather than the <for-each> approach (see below), I
wanted to see how the two methods compare in
terms of performance.
So, suppose I have the same input that Jeni uses, but making it a bigger XML
file (about 2000 entries):
<records>
<contact id="0001">
<title>Mr</title>
<forename>John</forename>
<surname>Smith</surname>
</contact>
<contact id="0002">
<title>Dr</title>
<forename>Amy</forename>
<surname>Jones</surname>
</contact>
<contact id="0002">
<title>Mr</title>
<forename>Brian</forename>
<surname>Jones</surname>
</contact>
<contact id="0002">
<title>Ms</title>
<forename>Fiona</forename>
<surname>Smith</surname>
</contact>
... repeating the above block ...
</records>
Using the <for-each> approach on my machine [Dell GX-240, Win2003,
XSelerator 2.6, MSXML 4.0], like this:
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform
<http://www.w3.org/1999/XSL/Transform> " version="1.0">
<xsl:key name="contacts-by-surname" match="contact" use="surname" />
<xsl:key name="contacts-by-surname" match="contact" use="surname" />
<xsl:template match="records">
<xsl:for-each select="contact[count(. | key('contacts-by-surname',
surname)[1]) = 1]">
<xsl:sort select="surname" />
<xsl:value-of select="surname" />,<br />
<xsl:for-each select="key('contacts-by-surname', surname)">
<xsl:sort select="forename" />
<xsl:value-of select="forename" /> (<xsl:value-of select="title" />)<br
/>
</xsl:for-each>
</xsl:for-each>
</xsl:template>
</xsl:transform>
showed that the transformation took up about 750 msec.
Then, using the template approach (adding just a bit of HTML), as follows:
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform
<http://www.w3.org/1999/XSL/Transform> " version="1.0">
<xsl:key name="contacts-by-surname" match="contact" use="surname" />
<xsl:template match="records">
<html>
<body>
<xsl:apply-templates select="contact[generate-id() =
generate-id(key('contacts-by-surname', surname))]" mode="groups"/>
</body>
</html>
</xsl:template>
<xsl:template match="contact" mode="groups">
<ul>
<xsl:value-of select="surname"/>,<br/><xsl:apply-templates
select="key('contacts-by-surname', surname)"/>
</ul>
</xsl:template>
<xsl:template match="contact">
      <xsl:value-of
select="forename"/> (<xsl:value-of select="title"/>)<br/>
</xsl:template>
</xsl:transform>
which does practically the same, it took only about 50 msec, which means a
performance gain of 750/50 = 15 times better!!
I haven't been able yet to test using the .NET XslTransform class, but that
will come in a later stage...
So for big input files and using MSXML 4.0, I would rather use the second
approach.... wouldn't you all agree?
And if so, shouldn't the second method not be the first (and preferred)
method mentioned by Jeni (after all, everyone points to that page at first
instance)?
<prs/>
http://www.pietsieg.com <http://www.pietsieg.com/>
http://www.pietsieg.com/dotnetnuke
Contributor on www.ASPToday.com <http://www.asptoday.com/>
Co-author on "Professional ASP.NET XML with C#", July 2002 by Wrox Press
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