May 26, 2021 Apache Pig
The LIMIT operator is used to get a limited number of groups from a relationship.
The syntax of the LIMIT operator is given below.
grunt> Result = LIMIT Relation_name required number of tuples;
Suppose you have a file called pig_data in the HDFS directory /student_details.txt, 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
The relationship
student_details loads
this file into
pig, 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 relationships in descending order based on the student's age and store them in another relationship called limit_data using the ORDER BY operator, as shown below.
grunt> limit_data = LIMIT student_details 4;
Use the DUMP operator to validate the relationship limit_data, as shown below.
grunt> Dump limit_data;
It produces the following output, showing the relationship 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)