title: Dynamodb query - OR condition in KeyConditionExpression
body: <p>I have a DynamoDB table with <code>feed_guid</code> as the global secondary index. I want to query with a set of <code>feed_guid</code> in that table. Since <code>feed_guid</code> is not my primary keys, I can't use <code>getBatchItem</code>. When I tried the following method, I got this error:</p>
  
  <blockquote>
    <p>Invalid operator used in KeyConditionExpression: OR</p>
  </blockquote>
  
  <pre class="lang-php prettyprint-override"><code>    $options = array(
                  'TableName' =&gt; 'feed',
                      'IndexName' =&gt; 'GuidIndex',
                      'KeyConditionExpression' =&gt; 'feed_guid = :v_guid1 or feed_guid = :v_guid2',
  
                      'ExpressionAttributeValues' =&gt;  array (
                          ':v_guid1' =&gt; array('S' =&gt; '8a8106e48bdbe81bf88d611f4b2104b5'),
                          ':v_guid2' =&gt; array('S' =&gt; '19cab76242a6d85717de64fe4f8acbd4')
                      ),
                      'Select' =&gt; 'ALL_ATTRIBUTES',
                  );
                  $response = $dynamodbClient-&gt;query($options);
  </code></pre>