Re: Speeding up processing (with sablotron or saxon)
At 01:33 PM 7/12/2004, you wrote:
ok I have a piece of XSLT that processes a large XML file into smaller chunks. The problem I have is that the deeper down into the XML file I am processing the longer it takes. Is this just due to the way XSLT parsers work or can I tweak my XSL file so it processes faster?
... this for-each is expensive. You are traversing the entire document looking for 'resource' elements; each one you find is examined by looking at all its preceding elements and comparing their @swgcraft_id attributes. When you have lots of elements, lots and lots of them are compared. (n^2 performance.)
Since this happens every time the template is matched (which could itself be lots of times), it adds up -- especially for the later nodes in your set (as you noticed).
An easy tweak to improve performance would be to use keys to de-duplicate instead of doing it by hand on the preceding:: axis.
<xsl:key name="resource-by-id" match="resource" use="@swgcraft_id"/>
<xsl:variable name="resources" select="//resource"/>
(binding //resource to a variable $resource so we don't have to retrieve it every single time)
then you can deduplicate in another variable declaration:
select="$resources[not(count(.|key('resources-by-id',@swgcraft_id)) = 1)]"/>
In English: $unique-resources is the collection of all resources which, when counted along with the first resource with the same swqcraft_id as themselves, amount to a single node (which is true only of the first one with each swgcraft_id).
This ought to help quite a bit.
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