Comp150CPA: Clouds and Power-Aware Computing
Classroom Exercise 8
Pig and Data Transformation
Spring 2011

group member 1: ____________________________ login: ______________

group member 2: ____________________________ login: ______________

group member 3: ____________________________ login: ______________

group member 4: ____________________________ login: ______________

group member 5: ____________________________ login: ______________

In class we have studied the Pig language for Map/Reduce and its basic transformations. Let's explore the latter in more detail. Suppose that inside Pig, we have

grunt> DUMP x; ... Success!! (George,Bear) (Frank,Dog) (George,Bear) (Bill,Cat) (Amy,Bear) grunt> DESCRIBE x x: {name: chararray, species: chararray}

grunt> DUMP y; ... Success!! (Bear,Hugs) (Dog,Barks) (Dog,Growls) (Cat,Purrs) (Bear,Growls) grunt> DESCRIBE y x: {species: chararray, action: chararray}

1. What is printed by the following scripts?

   1. z = FOREACH x GENERATE name,$0; 
      DUMP z; 
      

      
      
      
      
      
      

   2. z = FILTER y BY action=='Growls'; 
      DUMP z; 
      

      
      
      
      
      
      

   3. z = GROUP y by species; 
      DUMP z; 
      

      
      
      
      
      
      

   4. z = JOIN x BY species,y BY species; 
      DUMP z; 
      

      
      
      
      
      
      

   5. z = JOIN x BY species,y BY species; 
      w = FOREACH z GENERATE $0,$3; 
      DUMP w; 
      
       
       
       
       
      
      

2. (Advanced) Why is execution delayed as long as possible in Pig?