Speeding up collection()

hi list

I'm using collection() function with wild cards and regex to generate
a list of document filenames:

<xsl:for-each select="for $x in
collection(iri-to-uri('someDir/?select=*.xml')) return
saxon:discard-document($x)">
 <filename href="{tokenize(document-uri(.), '/')[last()]}"/>
</xsl:for-each>

It works fine but it takes a lot of time loading the documents.

How can I speed up the process, considering that I donbt really need
to load the documents, I just want there URLs returned?

Cheers,
Jesper Tverskov