the foreach operator is used to generate specified data transformations based on the column data.

syntax

given below is the syntax of foreach operator.

grunt> relation_name2 = foreach relatin_name1 generate (required data);

example

assume that we have a file named student_details.txt in the hdfs directory /pig_data/ as shown below.

student_details.txt

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

and we have loaded this file into pig with the relation name student_details as shown below.

grunt> 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);

let us now get the id, age, and city values of each student from the relation student_details and store it into another relation named foreach_data using the foreach operator as shown below.

grunt> foreach_data = foreach student_details generate id,age,city;

verification

verify the relation foreach_data using the dump operator as shown below.

grunt> dump foreach_data;

output

it will produce the following output, displaying the contents of the relation foreach_data.

(1,21,hyderabad)
(2,22,kolkata)
(3,22,delhi)
(4,21,pune) 
(5,23,bhuwaneshwar)
(6,23,chennai) 
(7,24,trivendram)
(8,24,chennai)