在Pig Latin中生成计数值

Question

我正在尝试查找年龄介于19到60之间的用户数量。以下是示例查询

loadtable = load '/user/userdetails.txt' using PigStorage(',') AS (name:chararray,age:int);

filteredvalues = filter loadtable  by (age > 19 AND  age < 60);

grouped = GROUP filteredvalues ALL;

count = foreach grouped generate COUNT(grouped);

我收到以下错误“无效的标量投影：已分组：需要根据关系投影列，以便将其用作标量”

Answer 1

您必须计算过滤值而不是分组。

total = foreach grouped generate COUNT(filteredvalues);

Answer 2

示例 userdetails.txt：

Robin,85

BOB,55

Maya,23

Sara,45

David,23

Maggy,22

Robert,75

Syam,23

Mary,25

Saran,17

Stacy,19

Kelly,22

<强>代码：

grunt> loadtable = load '/user/userdetails.txt' using PigStorage(',') AS (name:chararray,age:int);

grunt> filteredvalues = filter loadtable  by (age > 19 AND  age < 60);

grunt> grouped = GROUP filteredvalues ALL;

grunt> count = foreach grouped generate COUNT(filteredvalues);

grunt> dump count;

  

始终在群组关系或行李之前执行计数，否则会抛出：   ＆＃34;标量投影无效：已分组：需要投影列   从它的关系中用作标量＆＃34;