Apache Pig - Foreach Operator
The FOREACH operator is used to generate specified data transformations based on the column data.
Given below is the syntax of FOREACH operator.
grunt> Relation_name2 = FOREACH Relatin_name1 GENERATE (required data);
Assume that we have a file named student_details.txt in the HDFS directory /pig_data/ as shown below.
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;
Verify the relation foreach_data using the DUMP operator as shown below.
grunt> Dump foreach_data;
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)