XQuery - Query to retrieve all exact duplicates title-date values

find-title-date-duplicates.xqy

xquery version "1.0-ml";

(: 8/6/13 Query to retrieve all exact duplicates title-date values (using one of Priscilla Walmsley's functx XQuery functions :)  

declare namespace ia = "http://my.local.namespace";
declare namespace m = "http://www.loc.gov/MARC21/slim";

declare namespace functx = "http://www.functx.com"; 
declare function functx:non-distinct-values 
  ( $seq as xs:anyAtomicType* )  as xs:anyAtomicType* {
       
   for $val in distinct-values($seq)
   return $val[count($seq[. = $val]) > 1]
 } ;

let $items := 
    <items>{ let $titleDateSeq :=
                  let $docs := xdmp:directory("/ia-xml/q/", "infinity")
                  for $doc in $docs
                  let $date := $doc/ia:doc/ia:metadata/ia:date
                  let $title := $doc/ia:doc/ia:metadata/ia:title
                  let $vol := $doc/ia:doc/ia:metadata/ia:volumeInfo
                  where fn:not($vol)
                  order by $title
                  return <item>
                           <title>{ fn:normalize-space($title) }</title>
                           <date>{ fn:normalize-space($date) }</date>
                         </item>
             return $titleDateSeq }</items>
order by $items/item/title
(: Return value is title-date combination that appears more than once (i.e., exact duplicate title-date values) :)
return functx:non-distinct-values($items/item)