如何在 apache pig 下从一个包中找到所有可能的排列 [英] How To Find All Possible Permutations From A Bag under apache pig

问题描述

我正在尝试使用 apache pig 找到所有可能的组合，我能够生成排列，但我想消除我编写此代码的值的复制:

i'm trying to find all combinations possible using apache pig, i was able to generate permutation but i want to eliminate the replication of values i write this code :

A = LOAD 'data' AS f1:chararray;
DUMP A;
('A')
('B')
('C')
B = FOREACH A GENERATE $0 AS v1;
C = FOREACH A GENERATE $0 AS v2;
D = CROSS B, C;

我得到的结果是:

 DUMP D;
('A', 'A')
('A', 'B')
('A', 'C')
('B', 'A')
('B', 'B')
('B', 'C')
('C', 'A')
('C', 'B')
('C', 'C')

但我试图获得的结果就像波纹管

but what i'm trying to obtain the result is like bellow

DUMP R;
('A', 'A')
('A', 'B')
('A', 'C')
('B', 'B')
('B', 'C')
('C', 'C')

我该怎么做?我避免使用字符比较，因为一个字符串可能在多于一行中出现多次

how can i do this? i avoid to use comparison of characters because it's possible to have multiple occurrences of a string in more than a line

推荐答案

您可以通过 FILTER D 删除不需要的行.例如

You can FILTER D to remove the rows you don't want. For example

A = load 'testdata.txt';
B = foreach A generate $0;
C = Cross A, B;
D = filter C by $0 <= $1;
dump D;

打印出来

(C,C)
(B,C)
(B,B)
(A,C)
(A,B)
(A,A)

当'testdata.txt'有

when 'testdata.txt' has

A
B
C

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