Re: [xsl] Selecting multi-existant elements only once

[Joerg Heinicke <joerg.heinicke@xxxxxx>]

Tom already said, that you can use keys, which I prefer in general. But 
even without them your code can be optimized. Sorry, but you chosed the 
poorest one ;-)

> <xsl:for-each select="//departement/profession[not(desc=preceding::desc)]">

For *every* node on *every* level (independent of some processor 
specific optimizations) the conditions will be evaluated. This means 
every node will be tested for:

- name is profession
- parent is departement
- the string value of a node desc is compared to again *every* preceding 
node on *every* level with name desc

If you change it only a bit, the code will at least in larger lists much 
faster:

<xsl:for-each select="/departement/profession[not(desc = 
preceding-sibling::profession/desc)]">

The removing of the '//' reduces the <profession> elements exactly to 
only the elements on the second "level" (there is no "level" in XML, but 
I think you know what I mean: only one ancestor element). And the using 
of preceding-sibling axis reduces the necessary tests in the predicate 
more or less enormously, because you can tell the processor exactly 
where to find the desc elements and again it must not search them on 
every "level".

At the end the key solution:

<xsl:key name="professions" match="profession" use="desc"/>

<xsl:for-each select="/department/profession[generate-id() = 
generate-id(key('professions', desc))]">
  <xsl:value-of select="."/>
</xsl:for-each>

Regards,

Joerg

> I wrote:
> > Hi all,
> >
> > I've got a XML-File with following structure. There are different 
> > departements and in each departement there are different professions. 
> > I want to have every profession of all departement once... If there is 
> > a Manager in departement a and departement b, "Manager" should only be 
> > printed out once...
> >
> > How can I do that?
> >
> > [...]
> > <departement>
> >  <profession>
> >    <desc>Manager</desc>
> >    <salary>5000</salary>
> >  </profession>
> >
> >  <profession>
> >    <desc>Assistant</desc>
> >    <salary>3000</salary>
> >  </profession>
> >
> >  <profession>
> >    <desc>Employee</desc>
> >    <salary>2000</salary>
> >  </profession>
> > </departement>
> >
> > <departement>
> >  <profession>
> >    <desc>Manager</desc>
> >    <salary>5000</salary>
> >  </profession>
> >
> >  <profession>
> >    <desc>Worker</desc>
> >    <salary>2000</salary>
> >  </profession>
> > </departement>
> >
> > [...]
> >
> > Thanks for your help !
> >
> > Sorin


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