Top N per-group [String,String]

Select for each group the top-N results. This blocks requires a list of pairs [STRING,STRING] 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.

• SOURCE [STRING,STRING]: the list of pairs to filter. Distinct values in the first column identify groups

• RESULT [STRING,STRING]: the top-N for each group

• N: the number of results to return