What is the importance of using key value pairs in mapreduce?

Question

I'm starting to draw. Everywhere I see that only mapreduce uses key-value pairs. But I see no clear reason to use key-value pairs.

Thanks in advance!

Answer 1

Hadoop is mainly used for data analysis. In data analysis, we look at statistical and / or logical methods for describing and illustrating, condensing and repeating and evaluating data. We do not modify the data in any way.

Hadoop , . , . , .

, , . , - , , (Key) ().

Answer 2

, group by , , , , - .

, ,

file1.txt
1 
2
3
file2.txt
4
5
6

file1.txt ​​   1 ( ) 1 ()   2 ( ) 2 ()   3 ( ) 3 ()

(, ) :

file1 as key 3 as value

file2 as key 6 as value

file1 3
file2 6

, :

MAX 6

Answer 3

. compper . (, 1) mapper.Now , . , , hasoop , - , - . , , , .