hadoop - Apache PIG - 按 ID 计数(*)分组并创建排名

Question

各位专家好，

我有这个数据集:

Field_A Field_B    DATE
John     1       01-01-2016
John     1       05-01-2016
Cate     1       05-01-2016
Cate     4       01-01-2016
Cate     6       05-01-2016
Perdi    4       01-01-2016

我正在尝试计算每个 Field_A 的计数 (*) 并根据字段 A 和日期创建排名。基本上我想返回这个:

Field_A Count   Rank    Field_B
John      2      1        1
John      2      2        1
Cate      3      3        1
Cate      3      4        4
Cate      3      3        6
Perdi     1      5        4

为此，我正在尝试使用以下代码:

DATA  = load '...'
AS
          (Field_A:Int, 
          FIELD_B:Int,
          DATE:CHARARRAY);
A = rank DATA BY Field_A;
B = GROUP A BY $0;
C = foreach B {
     CNT = COUNT(A.Field_A);
     generate $0, CNT;
}
D = join A by $0, C by $0;
E = rank D BY DATE,Field_A DENSE;
F = foreach E generate $0 AS RANK,Field_A,CNT;
DUMP F;

但我收到以下错误:

<file script.pig, line 35, column 69> Invalid field projection. Projected field [CNT] does not exist in schema;

我该如何解决这个问题？

非常感谢!

Answer 1

C = foreach B {
     generate group as Field_A, COUNT(A) as CNT;
}