Re: [xsl] Which is less expensive group by or select distinct-values

["Tony Graham tgraham@xxxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

On 15/07/2016 20:20, dvint@xxxxxxxxx wrote:
> So I have a large document that I need to pull a list of unique values
> from a given element. These are taxonomy and term tag values from a 4,000
> topic collection of DITA content.
>
> Without knowing how these are implemented, is there something I should be
> able to intuit just from the spec? This is some code that I inherited and
> it wouldn't have been how I would have attacked the problem:
>
> <xsl:variable name="TermList">
> <xsl:value-of select="distinct-values(.//term[not(@keyref)])"
> separator=", " />
> </xsl:variable>
> <data type="topicreport" name="WDTermList">
>   <xsl:for-each select="tokenize(normalize-space($TermList), ', ')">
> 	<xsl:sort select="." />
> 	<xsl:value-of select="."/>
>          <xsl:if test="position() != last()">, </xsl:if>
>    </xsl:for-each>
> </data>

Another option that you could try to see how it affects memory usage [1]:

<xsl:key name="terms" match="term[empty(@keyref)]" use="true()" />

<data type="topicreport" name="WDTermList">
   <xsl:value-of separator=", ">
       <xsl:perform-sort select="distinct-values(key('terms', true()))">
           <xsl:sort select="." />
       </xsl:perform-sort>
   </xsl:value-of>
</data>

(borrowing the xsl:perform-sort idea from Martin Honnen, and assuming 
that the context node is the document element.)

Regards,


Tony Graham.
--
Senior Architect
XML Division
Antenna House, Inc.
----
Skerries, Ireland
tgraham@xxxxxxxxxxxxx


[1] Unless and until Michael Kay advises that using the xsl:key instead 
of '//' makes no difference in Saxon.