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What is Count Function in Apache Pig ?

  • The COUNT() function used in Apache Pig is used to get the number of elements in a bag.
  • The COUNT() function ignores all the tuples which is having a NULL value in the first field while counting the number of tuples given in a bag
  • The COUNT() function returns the number of rows that matches a specified criteria.
  • The COUNT() function returns the number of values which is given in a set of values.
  • The COUNT() function counts the number of cells that contain numbers, and also counts the numbers which are written within the list of arguments.
 Apache Pig Count() Function

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Pig Operations - Aggregation

  • build-in functions e.g. AVG, COUNT, COUNT_STAR, MAX, MIN, SUM
  • possibility to implement custom UDFs
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    grunt> COUNT(expression)



    • We have loaded the into Pig with the relation name wikitechy_employee_details which is given below:
    grunt> employee_details = LOAD 'hdfs://localhost:9000/pig_data/wikitechy_employee_details.txt' USING PigStorage(',')
       as (id:int, firstname:chararray, lastname:chararray, age:int, phone:chararray, city:chararray, gpa:int);

    Calculating the Number of Tuples

    • We can use the built-in function COUNT() to calculate the number of tuples which is given in a relation.
    • We need to group the relation wikitechy_employee_details using the Group All operator, and store the result in the relation name employee_group_all which is given below:
    grunt> employee_group_all = Group wikitechy_employee_details All;
    • It will produce a relation for calculating the number of tuples which is given below:
    • We can calculate number of tuples and records which is given in the relation.
    grunt> employee_count = foreach employee_group_all  Generate COUNT(wikitechy_employee_details.gpa);


    grunt> Dump employee_count;



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