Hadoop Secondary Sort example using playing cards. This code example uses the new API.
hearts 9
spades 10
hearts 5
diamonds 5
hearts 8
hearts 3
clubs 9
hearts 1
clubs 5
clubs 3
diamonds 7
diamonds 8
spades 9
spades 1
We want a reducer call with all of the values for a single suit in sorted order. The reducer calls should look like:
####R0
HEARTS,[1,3,5,8,9]
####R1
DIAMONDS,[5,7,8]
####R2
SPADES,[1,9,10]
####R3
CLUBS,[3,5,9]
To accomplish this goal, you need to use a Secondary Sort. This code gives an example of that with comment in the code showing what is happening.