Newbie, learning the hadoop concepts. Based on my understanding the mapper can emit any number of keys and values but they have to be same type. Based on my understanding option 1 looks good, but some website are mentioning it wrong. Can someone confirm this.
For each input key-value pair, mappers can emit:
As many intermediate key value pairs as desired, as long as all the keys have the same type and all the values have the same type
As many intermediate key-value pairs as desired. There are no restrictions on the types of those key-value pairs (i.e., they can be heterogeneous)
As many intermediate key-value pairs as desired, but they cannot be of the same type as the input key-value pair
One intermediate key value pair, but of the same type
