Top N per-group
Description
Select for each group the top-N results.
This blocks requires a list of pairs [OBJ,OBJ] as the input.
The groups are created on the first column, thus the second column is grouped by the first.
The results are also returned as a list of pairs. Thus, each member of the group as a separate result.
Input
SOURCE [OBJ,OBJ]: the list of objects pairs to filter. Distinct values in the first column identify groups
Output
RESULT [OBJ,OBJ]: the top-N objects for each group
Parameters
N: the number of results to return