Apache Pig - Foreach Operator


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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) 


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