Apache Pig - Filter Operator


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The FILTER operator is used to select the required tuples from a relation based on a condition.

Syntax

Given below is the syntax of the FILTER operator.

grunt> Relation2_name = FILTER Relation1_name BY (condition);

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 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';

Verification

Verify the relation filter_data using the DUMP operator as shown below.

grunt> Dump filter_data;

Output

It will produce the following output, displaying the contents of the relation filter_data as follows.

(6,Archana,Mishra,23,9848022335,Chennai)
(8,Bharathi,Nambiayar,24,9848022333,Chennai)


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