Apache Pig - Distinct Operator


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The DISTINCT operator is used to remove redundant (duplicate) tuples from a relation.

Syntax

Given below is the syntax of the DISTINCT operator.

grunt> Relation_name2 = DISTINCT Relatin_name1;

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,9848022337,Hyderabad
002,siddarth,Battacharya,9848022338,Kolkata 
002,siddarth,Battacharya,9848022338,Kolkata 
003,Rajesh,Khanna,9848022339,Delhi 
003,Rajesh,Khanna,9848022339,Delhi 
004,Preethi,Agarwal,9848022330,Pune 
005,Trupthi,Mohanthy,9848022336,Bhuwaneshwar
006,Archana,Mishra,9848022335,Chennai 
006,Archana,Mishra,9848022335,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, phone:chararray, city:chararray);

Let us now remove the redundant (duplicate) tuples from the relation named student_details using the DISTINCT operator, and store it as another relation named distinct_data as shown below.

grunt> distinct_data = DISTINCT student_details;

Verification

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

grunt> Dump distinct_data;

Output

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

(1,Rajiv,Reddy,9848022337,Hyderabad)
(2,siddarth,Battacharya,9848022338,Kolkata) 
(3,Rajesh,Khanna,9848022339,Delhi) 
(4,Preethi,Agarwal,9848022330,Pune) 
(5,Trupthi,Mohanthy,9848022336,Bhuwaneshwar)
(6,Archana,Mishra,9848022335,Chennai)


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