Question

SPLIT 运算符

Pig Latin的SPLIT运算符用于关系分成两个或更多的关系。
语法
下面给出的是SPLIT运算符的语法。

grunt> SPLIT Relation1_name INTO Relation2_name IF (condition1), Relation2_name (condition2)

假设我们在HDFS目录/pig_data/中有一个名为student_details.txt的文件，如下所示。

001,Rajiv,Reddy,21,9848022337,Hyderabad
002,siddarth,Battacharya,22,9848022338,Kolkata
003,Rajesh,Khanna,22,9848022339,Delhi 
004,Preethi,Agarwal,21,9848022330,Pune 
005,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar 
006,Archana,Mishra,23,9848022335,Chennai 
007,Komal,Nayak,24,9848022334,trivendram 
008,Bharathi,Nambiayar,24,9848022333,Chennai

并且我们已经将该文件加载到Pig中，关系名称为student_details，如下所示。

student_details = LOAD 'hdfs://localhost:9000/pig_data/student_details.txt' USING PigStorage(',')
   as (id:int, firstname:chararray, lastname:chararray, age:int, phone:chararray, city:chararray);

现在让我们将该关系分为两个，一个列出年龄小于23岁的雇员，另一个列出年龄在22至25岁之间的雇员。

SPLIT student_details into student_details1 if age<23, student_details2 if (22 < age and age > 25);

验证
如下所示，使用DUMP运算符验证关系Student_details1和student_details2。

grunt> Dump student_details1;  
grunt> Dump student_details2;

它将产生以下输出，分别显示关系student_details1和student_details2的内容。

grunt> Dump student_details1; 
(1,Rajiv,Reddy,21,9848022337,Hyderabad) 
(2,siddarth,Battacharya,22,9848022338,Kolkata)
(3,Rajesh,Khanna,22,9848022339,Delhi) 
(4,Preethi,Agarwal,21,9848022330,Pune)
grunt> Dump student_details2; 
(5,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar) 
(6,Archana,Mishra,23,9848022335,Chennai) 
(7,Komal,Nayak,24,9848022334,trivendram) 
(8,Bharathi,Nambiayar,24,9848022333,Chennai)