title: In Google BigQuery, how to get storage size of a partition in time-partitioned table?
body: <p>I can query for storage size of a table in BigQuery using <code>SELECT size_bytes FROM dataset.__TABLES__ WHERE table_id='mytable'</code>, but this only works for finding total size of table. How to get size of a specific partition from a time-partitioned table, for example I want to find out how much data is stored in mytable$20180701. </p>
  
  <p>I know I can for example copy that partition to a non-partitioned table and use the method above, but I feel this can't be the right method.</p>