title: How to generate a row number in pig?
body: <p>I'm using pig for data preparation, and I faced a problem which seems easy but I can't deal with:</p>
  
  <p>for example, I have a column of names</p>
  
  <pre><code>name
  ------
  Alicia
  Ana
  Benita 
  Berta 
  Bertha 
  </code></pre>
  
  <p>then how can I add a row number for each name? the result would be like this:</p>
  
  <pre><code>name    |  id
  ----------------
  Alicia  |  1
  Ana     |  2
  Benita  |  3
  Berta   |  4
  Bertha  |  5
  </code></pre>
  
  <p>Thank you for reading this question!</p>