Writing Map-Reduce Views


#1

Hi all, I’m trying to create a Map Reduce view as per the following scenario -

Map would emit key value-pair as :-
(Key1, 1), (Key1,4) , (Key1,3), (Key1,5), (Key1,5), (Key2,1), (Key3,6) (Key3,2) …

and after Reduce, expected output is the Maximum value for each key:
(Key1, 5)
(Key2, 1)
(Key3, 6)
Number of Key-value pairs are in hundreds currently. But it’s expected to be in the range of thousands.
Can some please help me in writing the reducer for the above scenario. Thanks


#2

Hey. In the map function, you can emit(Key, value) as the pair, and use the built it _STAT as the reduce function. While querying, if you want the global maximum, set group=false and if you want the maximum per key, set group=true.

Regards,
Aman.