title: Conditional update in Amazon local dynamodb
body: <p>I've put following object in Local Dynamo DB.</p>
  
  <pre><code>class LicenseEntitilement {
  
  String featureName;       // Primary key
  int EntitilementCount;
  int UsageCount;
  }
  </code></pre>
  
  <p>I need to do conditional update with following expression -</p>
  
  <p>Conditional expression is : (UsageCount + askedCount) &lt; EntitilementCount
  askedCount is an Integer.</p>
  
  <p>(UsageCount and EntitlementCount values are in DB and askedCount is local variable.)</p>
  
  <p>Update expression is: UsageCount = UsageCount + askedCount</p>
  
  <p>It's throwing an exception that '+' is not allowed in conditional expression.  Is there any way to achieve this conditional update?</p>