The FILTER operator is used to select the required tuples from a relation based on a condition.
Given below is the syntax of the FILTER operator.
grunt> Relation2_name = FILTER Relation1_name BY (condition);
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 use the Filter operator to get the details of the students who belong to the city Chennai.
filter_data = FILTER student_details BY city == 'Chennai';
Verify the relation filter_data using the DUMP operator as shown below.
grunt> Dump filter_data;
It will produce the following output, displaying the contents of the relation filter_data as follows.