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What is TOMAP() function in Apache Pig ?

  • The TOMAP() function is used to converts key/value expression pairs into a map.
  • Needs an even number of expressions as parameters.
  • The elements must comply with map type rules.
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Syntax

grunt> TOMAP(key-expression, value-expression [, key-expression, valueexpression ...])

Example

  • Ensure that we have a file named wikitechy_emp_details.txt in the HDFS directory /pig_data/, as given below.

Wikitechy_emp_details.txt

111,Anu,22,newyork 
112,Bastin,23,Kolkata 
113,Cimen,23,Tokyo 
114,Darathy,25,London 
115,Enba,23,Bhuwaneshwar 
116,Favin,22,Chennai 
  • 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);
  • · You can take the name and age of each record as key-value pairs and convert them into map as given below.
grunt> tomap = FOREACH emp_data GENERATE TOMAP(name, age);

Verification

  • · Now you can verify the contents of the tomap relation using the Dump operator as given below.
grunt> DUMP tomap;

Output

  • The above statement stores the result in the relation named emp_data. 
([Anu#22])
([Bastin#23])
([Cimen#23])
([Darathy#25]) 
([Enba#23])
([Favin#22])

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