Why does Hadoop Mapper sort data?

Question

What I realize is that creating a key sorted list to be sent to the reducer is the mappers main objective. Then if the list is very big it needs to be partitioned in mapper so that it can be handled by reducer(I mean for a unique key the value list is huge then it needs to be partitioned), but why exactly does hadoop need to sort the keys in mapper. I was asked this question by some one and I couldn't fully convince him. I am just a beginner and was a bit curious . Any help is appreciated.

score 0 · Accepted Answer · edited May 23 '17 at 11:57

0

Sorting happens after mapper phase and before executing reducer job, you are not require to do it explicitly.

Please refer similar question

edited May 23 '17 at 11:57

Community

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answered Dec 19 '14 at 05:36

Sandy

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Why does Hadoop Mapper sort data?

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