hadoop - PIG Latin中FLATTEN运算符的目的是什么

A =将'data'加载为(x，y);

B =将'data'加载为(x，z);

C = A乘以x，B乘以x；

D = foreach C生成flatten(A)，flatten(b);

E = D组，A::x

以上陈述中确切完成的操作以及我们在实时场景中使用flatten的位置。

最佳答案

A = load 'input1'   USING PigStorage(',') as (x, y);
(x,y) --> (1,2)(1,3)(2,3)
B = load 'input2'  USING PigStorage(',') as (x, z);`
(x,z) --> (1,4)(1,2)(3,2)*/
C = cogroup A by x, B by x;`

result:

(1,{(1,2),(1,3)},{(1,4),(1,2)})
(2,{(2,3)},{})
(3,{},{(3,2)})


D = foreach C generate group, flatten(A), flatten(B);`

when both bags flattened, the cross product of tuples are returned.

result:
(1,1,2,1,4)
(1,1,2,1,2)
(1,1,3,1,4)
(1,1,3,1,2)

E = group D by A::x`

here your are grouping with x column of relation A.

(1,1,2,1,4)
(1,1,2,1,2)
(1,1,3,1,4)
(1,1,3,1,2)

关于hadoop - PIG Latin中FLATTEN运算符的目的是什么，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28472179/