Hi Peter, thank you for your answer. using pf:collection gives me a "Speicherzugriffsfehler" (/Segmentation fault)/ when executing the query you proposed. Is that a bug in MonetDB XML? replacing "pf:collection" by "fn:collection" leads to Trans 55.436 msec Shred 19.083 msec Query 29241.029 msec Print 0.207 msec Timer 29582.455 msec So it is basically the same query time :( Patrick

Hi,

How about:

smiles> { for $i in pf:collection("tu") where $i//xq:molecule/@id = "1" return <smile>{$i}</smile> } </smiles>

is that any faster?

Peter