MonetDB user defined function grouping

Hi all, I am trying to do a user defined function written in C++ which takes the whole table as a parameter, loads it into a vector structure, and then divides the data in some groups (duplicities will occur). How can I return the results of this grouping from the C function? Probably I'd like to store the group IDs in a separate table and create and then create an M:N table between the group IDs and the original records. Any help appreciated. Best regards, Jiri Nadvornik Astronomical Institute AV CR Stellar department Czech Republic <mailto:nadvornik.ji@gmail.com> nadvornik.ji@gmail.com