title: Talend increment counter
body: <p>I'm making a ETL in Talend that add data in a table.</p>
  
  <p>The table is for a old system and the primary key is not auto-incremental.
  So I have to get the maximum id plus one every time that I insert a value in the table.</p>
  
  <p>I'm trying to use a var in the Expression Builder:</p>
  
  <ul>
  <li>first I save the max and set in a context variable</li>
  <li><p>then in the Expression Builder:</p>
  
  <pre><code>Context.Max += 1
  </code></pre></li>
  </ul>
  
  <p>The problem is that every time I get the same id, I need to save the sum.</p>