Apache Pig - Describe Operator


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The describe operator is used to view the schema of a relation.

Syntax

The syntax of the describe operator is as follows −

grunt> Describe Relation_name

Example

Assume we have a file student_data.txt in HDFS with the following content.

001,Rajiv,Reddy,9848022337,Hyderabad
002,siddarth,Battacharya,9848022338,Kolkata
003,Rajesh,Khanna,9848022339,Delhi
004,Preethi,Agarwal,9848022330,Pune
005,Trupthi,Mohanthy,9848022336,Bhuwaneshwar
006,Archana,Mishra,9848022335,Chennai.

And we have read it into a relation student using the LOAD operator as shown below.

grunt> student = LOAD 'hdfs://localhost:9000/pig_data/student_data.txt' USING PigStorage(',')
   as ( id:int, firstname:chararray, lastname:chararray, phone:chararray, city:chararray );

Now, let us describe the relation named student and verify the schema as shown below.

grunt> describe student;

Output

Once you execute the above Pig Latin statement, it will produce the following output.

grunt> student: { id: int,firstname: chararray,lastname: chararray,phone: chararray,city: chararray }

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