In this session we look in more detail on how to extend hive with
1. custom mappers and reducers
2. Writing user defined functions (UDF) and aggregation functions (UDAF)
it will greatly help if you try to calculate number of male and female raters per genre in the movielens dataset before coming to this meetup. While you can easily do this for a single genre, try to write a single query that generates count of male and female raters for all the genres. Try not to write too many if else conditions.