[xsl] Merging elements within a range using a key

["Mike B" <mikeb0304@xxxxxxxxxxx>]

I have a working transformation which merges Row elements into the 
appropriate Category elements as shown, based on the range

          category/@s <= row/@r <= category/@e

This statement works,   <xsl:copy-of select="/view/results/row[@r &gt;= 
current()/@s and @r &lt;= current()/@e]" />  but seems to slow things down 
as data volume increases.

Is it possible to use a key to find elements within a range like this? I'm 
at a loss as to what the syntax might be.

Any suggestions are appreciated!

Thanks. Mike

Simplified Input document
------------------------------------
<view>
 <results>
   <row r="20">
     <col c="1">col 20.1 data</col>
   </row>
   <row r="21">
     <col c="1">col 21.1 data</col>
   </row>
   <row r="22">
     <col c="1">col 22.1 data</col>
   </row>
 </results>
 <category>
   <category s="18" e="19">cat a</category>
   <category s="20" e="21">cat b</category>
   <category s="22" e="25">cat c</category>
 </category>
</view>


Output document
------------------------
<view>
 <results>
   <category s="20" e="21">cat b
     <row r="20">
       <col c="1">col 20.1 data</col>
     </row>
     <row r="21">
       <col c="1">col 21.1 data</col>
     </row>
   </category>
   <category s="22" e="25">cat c
     <row r="22">
       <col c="1">col 22.1 data</col>
     </row>
   </category>
 </results>
</view>



Transformation - without a key
----------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>

   <xsl:output method="xml" encoding="utf-8" />

<xsl:template match="/view">
 <xsl:copy>
  <xsl:apply-templates select="@*|node()"/>
  <xsl:copy-of select="/view/category" />
 </xsl:copy>
</xsl:template>

<xsl:template match="results">
 <!--  do not copy old results to output -->
</xsl:template>

<xsl:template match="/view/category">
 <xsl:element name="results">
  <xsl:call-template name="copy-attributes">
   <xsl:with-param name="attributes" select="@*" />
  </xsl:call-template>
  <xsl:call-template name="copy-attributes">
   <xsl:with-param name="attributes" select="/view/results/@*" />
  </xsl:call-template>
  <xsl:apply-templates select="category" />
 </xsl:element>

</xsl:template>

<xsl:template match="category">

 <xsl:variable name="row-test">
  <!-- should be improved with a key -->
  <xsl:copy-of select="/view/results/row[@r &gt;= current()/@s and @r &lt;= 
current()/@e]" />
 </xsl:variable>

 <xsl:if test="string-length($row-test) > 0">
  <xsl:choose>
   <xsl:when test="category">

    <xsl:element name="{name()}">
     <xsl:call-template name="copy-attributes">
      <xsl:with-param name="attributes" select="@*" />
     </xsl:call-template>
     <xsl:value-of select="text()" />

     <xsl:apply-templates select="category"/>

    </xsl:element>
   </xsl:when>

   <xsl:otherwise>
    <xsl:element name="{name()}">
     <xsl:call-template name="copy-attributes">
      <xsl:with-param name="attributes" select="@*" />
     </xsl:call-template>
     <xsl:value-of select="text()" />

     <xsl:copy-of select="$row-test" />
    </xsl:element>
   </xsl:otherwise>
  </xsl:choose>
 </xsl:if>

</xsl:template>


<xsl:template name="copy-attributes">
 <xsl:param name="attributes" />

 <xsl:for-each select="$attributes">
  <xsl:attribute name="{name()}">
   <xsl:value-of select="." />
  </xsl:attribute>
 </xsl:for-each>

</xsl:template>

<xsl:template match="@*|node()">
 <xsl:copy>
  <xsl:apply-templates select="@*|node()"/>
 </xsl:copy>
</xsl:template>

</xsl:stylesheet>

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