Thank you @jcamachorodriguez for your reply and for creating HIVE-17668. I'm glad to know that I'm not alone :) I will try to analyze the log files of HS2 in order to dig the CBO problem. Although I've also arrived to the same conclusion that exposing the window function to the outer most query may alter the results, I'm still not able to figure out an example where pushing the predicates changes the results depending if a window function is present in the select statement or not... If you have any example showing this behavior, I would be grateful. Concerning FIRST_VALUE, according to my understanding, it will not respond to my needs: It will not filter the records. If I have 2 versions of the same record id, using FIRST_VALUE (on all the columns) will return both records with correct values and then I would use a distinct. I'm not sure it will be more efficient than a ROW_NUMBER + filter, correct me if I'm wrong... Regards, Christian ... View more