Re: [xsl] Lookup efficiency in XALAN?

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

J,

At 04:45 PM 11/20/2003, you wrote:
> I have to do some validation in my xsl.
>
> I'm doing the following type statement 20,000 times, and the lookup file is
> around 50,000  lines of  id's <id key="XXYYZZJ"/>.
>
> <xsl:when test="not(document('../master/ids-master.xml')/ids/id[@key=$id])">
>
> It works for a while, then dies with an out of memory error, and it sure is
> slow!

The first thing you should definitely do is collect the lookup ids into a 
variable, as in

<xsl:variable name="keys" 
select="document('../master/ids-master.xml')/ids/id/@key"/>

Then you can test your local ids against the keys in the variable, without 
parsing your lookup file every time (which it sounds like your processor 
might be doing):

<xsl:when test="not($id = $keys])">

Try that and see if it helps.

If Xalan is already optimizing the document() lookup and parse, you may get 
no gain from this technique -- but there's no way it could hurt.

XSLT keys could also help, but since your keys are in a separate document 
you'd have to switch contexts to use the XSLT key function, like so:

<xsl:key name="keys-by-id" match="id" use="@key"/>

<xsl:variable name="keyfile" select="document('../master/ids-master.xml')"/>

... and then

<xsl:for-each select="$keyfile">
  <xsl:when test="not(key('keys-by-id', $id))">...</xsl:when>
</xsl:for-each>

but whether this helps also will depend on your processor and what kind of 
smarts it has inside.

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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