Question

嗨专家，

我有这个数据集：

using (readNext = command.ExecuteReader())
{
  while (readNext.Read())
  {
     for (int x = 0; x < 5; x++)  // Where I am iterating throught each column
     {
       var nextValue = readNext.GetValue(x);
       // Code
     }
  }
}

我正在尝试计算每个Field_A的Count（*）并根据Field A和Date创建一个等级。基本上我想回复这个：

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

为此，我正在尝试使用此代码：

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

但我收到以下错误：

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;

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;
}

Answer 2

将Field_A更改为CHARARRAY并使用＆＃39; \ t＆＃39;文件，我对许多陈述的解决方案没有留下深刻印象，但它确实有效，

A = LOAD '/user/root/datex.txt' USING PigStorage('\t') AS (Field_A:CHARARRAY, FIELD_B:Int,DATE:CHARARRAY);
B = FOREACH A GENERATE  Field_A, FIELD_B, ToDate(DATE,'MM-dd-yyyy') as Datex;
D = GROUP B by Field_A;
E = FOREACH D GENERATE group , COUNT(B.Field_A) ;
F = join E by $0, B by Field_A;
G = FOREACH F GENERATE $0,$1,$3,$4
H = rank G by $0, $3 ;
Last = FOREACH H GENERATE $1 as FIELD_A, $2 as CNT, $0 as Rank , $3 AS FIELD_B;
DUMP

Apache PIG - 按ID分组（*）和创建排名

2 个答案: