[Exist-open] Index field - Computed field function access to the same collection?

[Lars S. <sch...@sa...>]

Hello,

I want to index a collection and need a field that contains specific 
computed values from the same collection.
I have various TEI XML files with different biblStruct types. Some of 
these files refer to other biblStructs via ref elements. I need the IDs 
of the biblStructs that point to the current, indexed biblStruct.
However, when I reindex the collection, the fields almost exclusively 
contain “empty” values.

Here the code:

<collection xmlns="http://exist-db.org/collection-config/1.0">
     <index xmlns:tei="http://www.tei-c.org/ns/1.0" 
xmlns:xs="http://www.w3.org/2001/XMLSchema">
         <lucene>
             <module uri="http://application.de/xquery/facet-utils" 
prefix="fu" 
at="xmldb:exist:///db/apps/application/modules/index-facet-utils.xqm"/>
             <text qname="tei:biblStruct">
                 <field name="workgroupid" 
expression="fu:get-workgroup-id(.)"/>
             </text>
         </lucene>
     </index>
</collection>


declare function fu:get-workgroup-id($biblStruct as element()) as 
xs:string* {
     let $corresp as xs:string := $biblStruct/@corresp/string()
     let $workgroupsIds as xs:string* := 
collection("/db/projects/application/data/bibls")//tei:biblStruct[@type 
eq 'dataset'][.//tei:ref[@type eq 'relDocRef']/@target/string() = 
$corresp]/@xml:id/string()
     let $workgroupsIdsJoined := string-join($workgroupsIds,';')
     return
         if($workgroupsIdsJoined ne "") then $workgroupsIdsJoined else 
"empty"
};

I assume that I do not have access to the same collection that is 
actually indexed or to specific attributes/elements (this case is not 
described/addressed/mentioned in either the documentation or the book), 
but the function takes far too long for live productive use.

Thanks for the help.

Best regards