Re: Practical Suggestion for XSLT Performance Improvement

[James Clark <jjc@xxxxxxxxxx>]

"Clark C. Evans" wrote:

> Here is a snippet:
> 
>    <xsl:for-each select="$product-list">
>      <xsl:variable name="product" select="." />
>         ...
>           <xsl:for-each select="$day-list">
>             <xsl:variable name="day" select="." />
>               ...
> 
>               <xsl:value-of
>                 select="sum(//price[../product=$product]
>                                    [../../../dow=$day])" /> .

I found your stylesheet ran a lot faster when I rewrote this as:

   <xsl:for-each select="$product-list">
     <xsl:variable name="product" select="." />
     <xsl:variable name="product-prices"
select="//price[../product=$product]"/>
        ...
          <xsl:for-each select="$day-list">
            <xsl:variable name="day" select="." />
              ...
               
              <xsl:value-of 
                select="sum($product-prices[../../../dow=$day])" />

I suspect a further improvement would be possible by using keys (not yet
implemented by XT).  Declare a key

  <xsl:key name="price-by-product" match="price" use="../product"/>

and then use

  key('price-by-product',$product)

instead of

  //price[product=$product]

James



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