[MAPREDUCE-2007] Is it possible that use ArrayList or other type instead Iterable when use reduce(Object, Iterable, Context)?

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 0.20.2
• Fix Version/s: 0.20.2
• Assignee: Unassigned
• Reporter: Han Hui Wen
• Created: 12/Aug/10 15:56
• Updated: 12/Aug/10 18:02
• Resolved: 12/Aug/10 18:02

Description

1) Sometimes We only need get the elements count of the input values of Reducer task,

but we have to iterate all the input values to calculate it.

2) Sometimes We only need get a few elements (for example top n,last n ,or random ) from the input values of Reducer task,

if it can use ArrayList or other type instead Iterable when use reduce(Object, Iterable, Context),it 's more conveniency.