[Monetdb-developers] group by on BATs

Hi, I have three BATs and I would like to create groups of pairs from the first two BATs and take the bitwise and for the tail values of each group according to the third BAT. I saw that there is a module for grouping operations in monetdb5/modules/kernel/group.mx. Is it the right one for my purpose? For the case of bitwise and is there any function that I could use or I should write my own like for example the GRPaggr_count() function in that file. Thanks, Babis