The CROSS operator computes the cross-product of two or more relations. This blog explains with example how to use the cross operator in Pig Latin.
Syntax
Given below is the syntax of the CROSS operator.
grunt> Relation3_name = CROSS Relation1_name, Relation2_name;
Example
Assume that we have two files namely customers.txt and orders.txt in the /pig_data/ directory of HDFS as shown below.
customers.txt
1,Ramesh,32,Ahmedabad,2000.00
2,Khilan,25,Delhi,1500.00
3,kaushik,23,Kota,2000.00
4,Chaitali,25,Mumbai,6500.00
5,Hardik,27,Bhopal,8500.00
6,Komal,22,MP,4500.00
7,Muffy,24,Indore,10000.00
orders.txt
102,2009-10-08 00:00:00,3,3000
100,2009-10-08 00:00:00,3,1500
101,2009-11-20 00:00:00,2,1560
103,2008-05-20 00:00:00,4,2060
And we have loaded these two files into Pig with the relations customers and orders as shown below.
grunt> customers = LOAD ‘hdfs://localhost:9000/pig_data/customers.txt’ USING PigStorage(‘,’)
as (id:int, name:chararray, age:int, address:chararray, salary:int);

grunt> orders = LOAD ‘hdfs://localhost:9000/pig_data/orders.txt’ USING PigStorage(‘,’)
as (oid:int, date:chararray, customer_id:int, amount:int);
Let us now get the cross-product of these two relations using the cross operator on these two relations as shown below.
grunt> cross_data = CROSS customers, orders;
Verification
Verify the relation cross_data using the DUMP operator as shown below.
grunt> Dump cross_data;
Output
It will produce the following output, displaying the contents of the relation cross_data.
(7,Muffy,24,Indore,10000,103,2008-05-20 00:00:00,4,2060)
(7,Muffy,24,Indore,10000,101,2009-11-20 00:00:00,2,1560)
(7,Muffy,24,Indore,10000,100,2009-10-08 00:00:00,3,1500)
(7,Muffy,24,Indore,10000,102,2009-10-08 00:00:00,3,3000)
(6,Komal,22,MP,4500,103,2008-05-20 00:00:00,4,2060)
(6,Komal,22,MP,4500,101,2009-11-20 00:00:00,2,1560)
(6,Komal,22,MP,4500,100,2009-10-08 00:00:00,3,1500)
(6,Komal,22,MP,4500,102,2009-10-08 00:00:00,3,3000)
(5,Hardik,27,Bhopal,8500,103,2008-05-20 00:00:00,4,2060)
(5,Hardik,27,Bhopal,8500,101,2009-11-20 00:00:00,2,1560)
(5,Hardik,27,Bhopal,8500,100,2009-10-08 00:00:00,3,1500)
(5,Hardik,27,Bhopal,8500,102,2009-10-08 00:00:00,3,3000)
(4,Chaitali,25,Mumbai,6500,103,2008-05-20 00:00:00,4,2060)
(4,Chaitali,25,Mumbai,6500,101,2009-20 00:00:00,4,2060)
(2,Khilan,25,Delhi,1500,101,2009-11-20 00:00:00,2,1560)
(2,Khilan,25,Delhi,1500,100,2009-10-08 00:00:00,3,1500)
(2,Khilan,25,Delhi,1500,102,2009-10-08 00:00:00,3,3000)
(1,Ramesh,32,Ahmedabad,2000,103,2008-05-20 00:00:00,4,2060)
(1,Ramesh,32,Ahmedabad,2000,101,2009-11-20 00:00:00,2,1560)
(1,Ramesh,32,Ahmedabad,2000,100,2009-10-08 00:00:00,3,1500)
(1,Ramesh,32,Ahmedabad,2000,102,2009-10-08 00:00:00,3,3000)-11-20 00:00:00,2,1560)
(4,Chaitali,25,Mumbai,6500,100,2009-10-08 00:00:00,3,1500)
(4,Chaitali,25,Mumbai,6500,102,2009-10-08 00:00:00,3,3000)
(3,kaushik,23,Kota,2000,103,2008-05-20 00:00:00,4,2060)
(3,kaushik,23,Kota,2000,101,2009-11-20 00:00:00,2,1560)
(3,kaushik,23,Kota,2000,100,2009-10-08 00:00:00,3,1500)
(3,kaushik,23,Kota,2000,102,2009-10-08 00:00:00,3,3000)
(2,Khilan,25,Delhi,1500,103,2008-05-20 00:00:00,4,2060)
(2,Khilan,25,Delhi,1500,101,2009-11-20 00:00:00,2,1560)
(2,Khilan,25,Delhi,1500,100,2009-10-08 00:00:00,3,1500)
(2,Khilan,25,Delhi,1500,102,2009-10-08 00:00:00,3,3000)
(1,Ramesh,32,Ahmedabad,2000,103,2008-05-20 00:00:00,4,2060)
(1,Ramesh,32,Ahmedabad,2000,101,2009-11-20 00:00:00,2,1560)
(1,Ramesh,32,Ahmedabad,2000,100,2009-10-08 00:00:00,3,1500)
(1,Ramesh,32,Ahmedabad,2000,102,2009-10-08 00:00:00,3,3000)

Apache Pig – Union Operator

The UNION operator of Pig Latin is used to merge the content of two relations. To perform UNION operation on two relations, their columns and domains must be identical.
Syntax
Given below is the syntax of the UNION operator.
grunt> Relation_name3 = UNION Relation_name1, Relation_name2;
Example
Assume that we have two files namely student_data1.txt and student_data2.txt in the /pig_data/ directory of HDFS as shown below.
Student_data1.txt
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.
Student_data2.txt
7,Komal,Nayak,9848022334,trivendram.
8,Bharathi,Nambiayar,9848022333,Chennai.
And we have loaded these two files into Pig with the relations student1 and student2 as shown below.
grunt> student1 = LOAD ‘hdfs://localhost:9000/pig_data/student_data1.txt’ USING PigStorage(‘,’)
as (id:int, firstname:chararray, lastname:chararray, phone:chararray, city:chararray);

grunt> student2 = LOAD ‘hdfs://localhost:9000/pig_data/student_data2.txt’ USING PigStorage(‘,’)
as (id:int, firstname:chararray, lastname:chararray, phone:chararray, city:chararray);
Let us now merge the contents of these two relations using the UNION operator as shown below.
grunt> student = UNION student1, student2;
Verification
Verify the relation student using the DUMP operator as shown below.
grunt> Dump student;
Output
It will display the following output, displaying the contents of the relation student.
(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)
(7,Komal,Nayak,9848022334,trivendram)
(8,Bharathi,Nambiayar,9848022333,Chennai)

So, this brings us to the end of blog. This Tecklearn ‘How to use Cross Operator and Union Operator in Pig Latin’ helps you with commonly asked questions if you are looking out for a job in Apache Pig and Big Data Domain.
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