[MAPREDUCE-4868] Allow multiple iteration for map

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.0.3-alpha, 3.0.0-alpha1
• Component/s: mrv2
• Assignee: Unassigned
• Reporter: Haifeng Chen
• Created: 11/Dec/12 02:26
• Updated: 12/May/16 18:23

Description

Currently, the Mapper class allows advanced users to override "public void run(Context context)" method for more control over the execution of the mapper, while Context interface limit the operations over the data which is the foundation of "more control".

One of use cases is that when I am considering a hive optimziation problem, I want to go two passes over the input data instead of using a another job or task ( which may slower the whole process). Each pass do the same thing but with a different parameters.

This is a new paradigm of Map Reduce usage and can be archived easily by extend Context interface a little with the more control over the data such as reset the input.