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Optimize an XSLT script
Added by Anonymous about 16 years ago
Legacy ID: #5547060
Legacy Poster: XmlStudent (xmlstudent80)
Hi everyone! I'm trying to learn XSLT and I have a doubt about a particular
transformation. It is the first time I write in this forum , please let me know if the
problem or the questions are not clear. Let's say that I have a source instance with two
sets of soccer players:
---------------------------------------------------source------------
<Players> <Player role="forward">
<name>Messi</name> </Player> <Player
role="forward">
<name>C.Ronaldo</name> </Player>
<Player role="striker">
<name>Messi</name> </Player> <Player
role="striker"> <name>Raul</name>
</Player> <Players>
--------------------------------------------------- the result that I want to get is a
list of forward/strikers players (a copy) without duplicates, that is:
---------------------------------------------------target------------
<Strikers> <Player>
<name>Messi</name> </Player>
<Player> <name>C.Ronaldo</name>
</Player> <Player>
<name>Raul</name> </Player>
<Strikers> --------------------------------------------------- I've been
able to write the following xsl script, but I suppose the complexity (thus the running
time) can be reduced. In the script the idea is:copy all the players marked as forward,
then copy all the players marked as stikers that were not marked as forward.
---------------------------------------------------XSL------------ <?xml
version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:pp="Paolo's functions"
xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xsl:output
method="xml" version="1.0"
encoding="UTF-8" indent="yes"/>
<xsl:function name="pp:is-node-in"
as="xs:boolean" > <xsl:param
name="node" as="node()?"/> <xsl:param
name="seq" as="node()"/>
<xsl:sequence select="some $nodeInSeq in $seq satisfies
($nodeInSeq/text()=$node/text())"/> </xsl:function> [...]
<xsl:for-each select=".[@role='forward']">
<xsl:apply-templates select="."/>
</xsl:for-each> <xsl:for-each
select=".[@sourceView='striker']"> <xsl:variable
name="innerCandidate" select="."/>
<xsl:if
test="not(pp:is-node-in($innerCandidate/homeName,/result/[@sourceView='Home2']/homeName))">
<xsl:apply-templates select="."/>
</xsl:if> </xsl:for-each> [...]
</xsl:template> <xsl:template name="normal"
match=""> <xsl:copy> <xsl:copy-of
select="./@[not((name()='sourceView'))]"/>
<xsl:value-of select="./text()"/>
<xsl:apply-templates select="*"/>
</xsl:copy> </xsl:template> </xsl:stylesheet>
------------------------------------------------------------------------------------------------
notice the 'is-node-in' function: is there anything better available in Saxon? notice
also the containmente test I do for each stiker element: this is like a very expensive
self join on the source Players set....any idea to improve it, leaving me the chance to
compare also players on more than 1 value? (say name and age) thanks in advance for you
help! -- paolo
Legacy ID: #5547330
Legacy Poster: Michael Kay (mhkay)
I would suggest that you ask XSLT coding questions on the xsl-list at
mulberrytech.com in future. This list is designed for questions that are specifically
Saxon support issues. Performance is product-specific, of course, but in this case I
think your questions are largely product-independent. I suspect that your is-node-in()
function should be testing for node identity rather than equality (but I'm not sure, I
haven't really tried to follow your logic in detail, and you haven't included it all,
and what you have included refers to things that aren't in your source, like an
@sourceView attribute). If I'm right, then <xsl:sequence select="some
$nodeInSeq in $seq satisfies ($nodeInSeq/text()=$node/text())"/> should
be <xsl:sequence select="some $nodeInSeq in $seq satisfies ($nodeInSeq
is $node)"/> which can be more succinctly expressed as
<xsl:sequence select="exists($nodeInSeq intersect
$seq)"/> On the other hand, if it really is an equality test you want,
then it can be written <xsl:sequence select="$nodeInSeq =
$seq"/> However, all this is probably irrelevant. What you are doing
looks like a simple grouping problem, and if you want to do it efficiently you should
use <xsl:for-each-group>.
Legacy ID: #5547541
Legacy Poster: XmlStudent (xmlstudent80)
Michael, thanks for your reply (and for your work on Saxon in general). You are
right, there were a couple of typos in my code: 'sourceView' value stand for 'role' and
the correct line test is: <xsl:if
test="not(pp:is-node-in($innerCandidate/name,/result/*[@role='forward']/name))">
-------------------------------------------------------------------------------- I've
been thinking about for-each-group, but I'm not sure it may help. If I understand
correctly, with for-each-group you can specify transformations as follows (for my
example): <xsl:for-each-group select="file"
group-by="@role"> <xsl:for-each
select="current-group()"> <xsl:value-of
select="@name"/> </xsl:for-each> but this
solution doesn't help in my case: 1. I need to take different actions depending on the
value of role, 2. the performance issue is due to the test line above, when I check for
each striker element if I had copied it in a previous step I'll try to post also on the
other web site, thanks for the pointer. -- Paolo
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