title: add where condition make MDX query slow (olap4j)
body: <p>I'm using <b>MONDRIAN</b> server and <b>OLAP4j</b> API in a Java Web application, i have a performance issues when adding a where close to my queries.
  MDX query like :</p>
  
  <pre><code>SELECT 
     CrossJoin(
       {[Product.ProductHierarchie].[AllProduct]}
     , {[Measures].[Quantity]}
     ) ON COLUMNS,
     [Client.ClientHierarchie].[AllClient].Children ON ROWS
  FROM [sales_data_cube]
  </code></pre>
  
  <p>0.3 second to be done. But when adding a where clause, like <br>
  <code>WHERE ([Period].&amp;[start_period]:[Period].&amp;[end_period])</code>,
  <br>to get the sales between a start/end periods, the query take more than <b>250 seconds</b> with a small fact table (8500 rows).</p>
  
  <p>What i should do to have a better performance?</p>
  
  <p>The application is running on a tomcat server with memory limit = 8GB, Data base server : MySQL 5.6.17</p>