Performance tuning - files already sorted

I have two XML files that I am merging together.  They contain <Product>s
which are already in a sorted order based on an element in them, <ID>.  The
files that I am mergine will have anywhere from 100 - 10,000 <Product>s.
This is extremely slow the way that I have implemented this:

     <xsl:for-each select="$YESTERDAY_FILE">
          <xsl:for-each select="key('ProdKey', $ID)">
               ... merging based on whether or not the children of the
Product match
          </xsl:for-each>
     </xsl:for-each>

Is there a way that I can speed this up?

Thanks in advance,
     Matt Youngblut



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