aggregation with complex function

Hello, I have an embedded python function which, given two integer parameters, after doing some stuff returns a table. I would like to group by a table by these two input parameter, and for each resulting group call the function. The result would be the concatenation of all the tables returned by the function. I understand that a thing like this would be very easy if the function returned just one value e.g.: select my_aggr_function(value1, value2) from table group by value1, value2 But how can I do this if my_aggr_function returns multiple rows?? Thank you, Stefano