title: Cassandra asks for ALLOW FILTERING even though column is clustering key
body: <p>Very new to Cassandra so apologies if the question is simple.</p>
  
  <p>I created a table:</p>
  
  <pre><code>create table ApiLog (
  LogId uuid,     
  DateCreated timestamp,
  ClientIpAddress varchar,
  primary key (LogId, DateCreated));
  </code></pre>
  
  <p>This work fine:</p>
  
  <pre><code>select * from apilog
  </code></pre>
  
  <p>If I try to add a where clause with the DateCreated like this:</p>
  
  <pre><code>select * from apilog where datecreated &lt;= '2016-07-14'
  </code></pre>
  
  <p>I get this:</p>
  
  <p><code>Cannot execute this query as it might involve data filtering and thus may have unpredictable performance. If you want to execute this query despite the performance unpredictability, use ALLOW FILTERING</code></p>
  
  <p>From other questions here on SO and from the tutorials on datastax it is my understanding that since the datecreated column is a clustering key it can be used to filter data.</p>
  
  <p>I also tried to create an index but I get the same message back. And I tried to remove the DateCreated from the primary key and have it only as an index and I still get the same back:</p>
  
  <pre><code>create index ApiLog_DateCreated on dotnetdemo.apilog (datecreated);
  </code></pre>