Re: Will Saxon 9 optimize or cache this so performance

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Subject: Re: Will Saxon 9 optimize or cache this so performance doesn't degrade?
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Tue, 05 Feb 2013 09:31:17 +0000

With optimization, it all depends....

You won't get any indexing optimizations. Those are done only for equality predicates, not for contains().

If $map is a global variable, then Saxon-EE will recognize this as an expression that depends only on global variables, and turn it into a global variable itself. Or at least it will if you remove the requirement to create a new copy of the nodes each time it's evaluated: change it to

<xsl:variable name="topicChapters" select="$map//*[contains(@class, ' bookmap/chapter ')]
              union $map//*[contains(@class, ' bookmap/appendix ')]
              union $map//*[contains(@class, ' bookmap/preface ')]"/>

unless for some reason you really want a fresh copy to be made each time.

But if $map is local, no such luck. Your best bet then would be to turn it into a memo function.

Michael Kay
Saxonica

On 05/02/2013 01:43, Steve Fogel wrote:

Hi, all...

I've got a PDF customization template that gets called maybe a couple of dozen
times during the processing of a DITA bookmap. It has the following code in it:

       &lt;xsl:variable name="topicChapters">
	   &lt;xsl:copy-of select="$map//*[contains(@class, ' bookmap/chapter ')]
               union $map//*[contains(@class, ' bookmap/appendix ')]
               union $map//*[contains(@class, ' bookmap/preface ')]"/>
       &lt;/xsl:variable>

This code will have to scan a good deal of the XML tree document represents the book. The
document will not change between each execution of the template.

Will Saxon optimize/cache this and not calculate it each time? I can always set
this variable in a parent template (that executes only once) and pass it into
this one. For readability however, it makes more sense to have this variable
where it is.

Thanks

Steve


Steve Fogel | Information Architect, Oracle Database | 650.506.4914
Oracle Server Technologies Information Development
500 Oracle Parkway | M/S 4op1126 | Redwood Shores, CA 94065

Current Thread
Will Saxon 9 optimize or cache this so performance doesn't degrade? Steve Fogel - 5 Feb 2013 01:44:04 -0000 Michael Kay - 5 Feb 2013 09:31:32 -0000 <=

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