Apache Pig - Limit Operator


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The LIMIT operator is used to get a limited number of tuples from a relation.

Syntax

Given below is the syntax of the LIMIT operator.

grunt> Result = LIMIT Relation_name required number of tuples;

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);

Now, let’s sort the relation in descending order based on the age of the student and store it into another relation named limit_data using the ORDER BY operator as shown below.

grunt> limit_data = LIMIT student_details 4; 

Verification

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

grunt> Dump limit_data; 

Output

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

(1,Rajiv,Reddy,21,9848022337,Hyderabad) 
(2,siddarth,Battacharya,22,9848022338,Kolkata) 
(3,Rajesh,Khanna,22,9848022339,Delhi) 
(4,Preethi,Agarwal,21,9848022330,Pune) 

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