title: Make existing bigquery table clustered
body: <p>I have a quite huge existing partitioned table in bigquery. I want to make the table clustered, at least for the new partition.</p>
  
  <p>From the documentation: <a href="https://cloud.google.com/bigquery/docs/creating-clustered-tables" rel="noreferrer">https://cloud.google.com/bigquery/docs/creating-clustered-tables</a>, it is said that we are able to <code>Creating a clustered table when you load data</code> and I have tried to load a new partition using clustering fields: <code>job_config.clustering_fields = ["event_type"]</code>.</p>
  
  <p>The load finished successfully, however it seems that the new partition is not clustered (I am not really sure how to check whether it is clustered or not, but when I query to that particular partition it would always scan all rows).</p>
  
  <p>Is there a good way to make clustering field for an existing partitioned table? </p>
  
  <p>Any comment, suggestion, or answer is well appreciated.</p>
  
  <p>Thanks a lot,
  Yosua</p>