Apache Pig - TOMAP()
The TOMAP() function of Pig Latin is used to convert the key-value pairs into a Map.
Given below is the syntax of the TOMAP() function.
grunt> TOMAP(key-expression, value-expression [, key-expression, valueexpression ...])
Assume we have a file named employee_details.txt in the HDFS directory /pig_data/, with the following content.
001,Robin,22,newyork 002,BOB,23,Kolkata 003,Maya,23,Tokyo 004,Sara,25,London 005,David,23,Bhuwaneshwar 006,Maggy,22,Chennai
We have loaded this file into Pig with the relation name emp_data as shown below.
grunt> emp_data = LOAD 'hdfs://localhost:9000/pig_data/employee_details.txt' USING PigStorage(',') as (id:int, name:chararray, age:int, city:chararray);
Let us now take the name and age of each record as key-value pairs and convert them into map as shown below.
grunt> tomap = FOREACH emp_data GENERATE TOMAP(name, age);
You can verify the contents of the tomap relation using the Dump operator as shown below.
grunt> DUMP tomap; ([Robin#22]) ([BOB#23]) ([Maya#23]) ([Sara#25]) ([David#23]) ([Maggy#22])