title: How exactly FLATTEN works in PIG
body: <p><strong>A:</strong>
      (1,2,3)
      (4,2,1)
      (8,3,4)
      (4,3,3)
      (7,2,5)
      (8,4,3)</p>
  
  <p><strong>B:</strong>
      (2,4)
      (8,9)
      (1,3)
      (2,7)
      (2,9)
      (4,6)
      (4,9)</p>
  
  <p><strong>C:</strong>
      (1,{(1,2,3)},{(1,3)})
      (4,{(4,2,1),(4,3,3)},{(4,6),(4,9)})
      (8,{(8,3,4),(8,4,3)},{(8,9)})</p>
  
  <p>Hi friends,
  For the above files A,B and C, can anyone explain what will be the result of the below statement ? 
  X = FOR EACH C GENERATE FLATTEN(A.($0,$1)), FLATTEN(B.$1);</p>
  
  <p>I am struggling really hard to know how flattens works.
  Thanks in advance!</p>