Hi, I have a stream source emitting key1, activity_a, secondKey1 key1, activity_b, secondKey2
key2, activity_a, secondKey1 key2, activity_b, secondKey2 ... The second key can be null. I would like to first groupby main key to get all the count of the activities. so i will get key1, count_activity_a, count_activity_b, secondKey key2, count_activty_a, count_activty_b, secondKey Then I would like to group by the second key, ignore all the secondKey non existing entries, and get all the count together, so the desired result would be secondKey1, count_activity_a, count_activity_b secondKey2, count_activity_a, count_activity_b How can I achieve this in Trident? The first step is pretty easy. However, i am not sure how to do the second grouping, since I need to filter out the secondkey non existing entries. But until the first level calculation is all done, i will not know whether it has second key or not. Thanks much! Chen
