RE: [xsl] Slow Transformation

Subject: RE: [xsl] Slow Transformation
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Wed, 19 Nov 2008 19:40:23 -0000
The lack of indentation here makes it very hard to see the structure, but
I'll try.

<xsl:template match="/">

That's really sloppy HTML. If you're generating HTML using XSLT, there's
really no excuse for not making it something that at least approximates to
valid HTML.

<xsl:for-each select="pmr6sum/item[count(. | key('d-due',due)[1])=1]">

You're doing Muenchian grouping here. That doesn't by itself explain why the
performance is bad, but you would improve your code and perhaps make the
problem more visible by using xsl:for-each-group instead.

<xsl:for-each select="pmr6sum/item[count(. | key('c-code',ccode)[1])=1]">
  <xsl:for-each select="../item[count(. | key('d-due',due)[1])=1]">
    <xsl:value-of select="format-number(sum(../item[(ccode=$c-code) and
(due=current()/due)]/book),'########')" />

I think this is the heart of your problem. For each item (well, each
distinct item) you are processing ../item - that is, all the sibling items;
and for each of these you have another .//item which is again processing all
the sibling items. So if you double the number of items, your code will take
8 times as long: it's O(n^3).

I'm not inclined to suggest improvements to this code without first
understanding something about your data and the requirements your code is
designed to meet. 

Michael Kay

> -----Original Message-----
> From: Eugene Bernard [mailto:eugene.bernard@xxxxxxxxx] 
> Sent: 19 November 2008 07:52
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] Slow Transformation
> Hi all,
> I am using the below xsl file to transform a xml file of size 
> approximately 3MB to a HTML file.
> The transformation takes more time...
> Can anybody help me to sort this out.
> Note : using java version "1.6.0_04" and saxon9

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