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What is TOP() function in Apache Pig ?

  • The TOP() function of Pig Latin is used to get the top N tuples of a bag.
  • To this function, as inputs, we have to pass a relation, the number of tuples you need, and the column name whose values are being compared.
  • This function will return a bag containing the required columns.


grunt> TOP(topN,column,relation)


  • Ensure we have a file named wikitechy_emp_details.txt in the HDFS directory /pig_data/, with the following content.


  • You have loaded this file into Pig with the relation name emp_data as given below.
grunt>emp_data = LOAD 'hdfs://localhost:9000/pig_data/ wikitechy_emp_details.txt' USING PigStorage(',')
   as (id:int, name:chararray, age:int, city:chararray);
  • Group the relation emp_data by age, and store it in the relation emp_group.
grunt> emp_group = Group emp_data BY age;

Now verify the relation emp_group using the Dump operator as given below.

grunt> Dump emp_group;
(23,{(118,Syam,23,Kolkata),(115,David,23,Bhuwaneshwar),(113,Cimen,23,Tokyo),(112,Bastin,23, Kolkata)}) 
(25,{(111,Anu,25,Bhuwaneshwar),(120,Vincent,25,London),(119,Mary,25,Tokyo),(114,Darathy, 25,London)})

Now, you can get the top two records of each group arranged in ascending order (based on id) as given below.

grunt> data_top = FOREACH emp_group { 
   top = TOP(2, 0, emp_data); 
   GENERATE top; 
  • In this instance we are retriving the top 2 tuples of a group having greater id.
  • Then we are retriving top 2 tuples basing on the id, we are passing the index of the column name id as second parameter of TOP() function.


You can verify the contents of the data_top relation using the Dump operator as given below.

grunt> Dump data_top;

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