title: BigQuery not dealing with timestamp in millisecond with partition column
body: <p>I have a unix timestamp column which is represented in millisecond in my csv file. Now when I insert this data in my bigQuery table and query it I get this error </p>
  
  <p><a href="https://stackoverflow.com/questions/50285385/bigquery-not-supporting-milliseconds-timestamps">bigQuery not supporting milliseconds timestamps</a></p>
  
  <p>Now I would like to make this column as a partition column. 
  I have a few questions 
  1) Even if I save it as int64, how can I make a partition column on this field?
  2) I would like to avoid duplicate tables. </p>