xquery grouping

Hi Basex, I have written a query on an xml file which contains 13000 nodes ,query does some grouping action on that xml,when I run that query it is taking huge amount of memory(1.5gb) and also processing time. PFA of xml file and the query.I have removed the nodes from xml for easy transfer,but in the original xml there will be around 13k <row/> tags Please suggest whether is there a way to reduce the memoru consumption. Thanks & Regards Sateesh.A