Java – MapReduce job without mapper

This may be a very basic question, but it is still helpful for many novices like me

Can I do Mr work without a mapper? Do we need to achieve this and the way to achieve this?

Solution

Identity mapper is a mapper that maps input directly to output

Suppose you have an input in the form of key value, and you have no relationship in the mapper stage. The only thing you want to do is group the values according to the key and aggregate the values in the reducer stage. You can use this mapper