title: BigQuery: How to use run_date in the query when back-filling
body: <p>I want to take data from yesterday's firebase analytics events table, transform the data and update an existing partitioned table with the same suffix as the origin events table.<br>
  For the destination table, I'm able to use a template: <code>shares_{run_time-24h|"%Y%m%d"}</code><br>
  But in the query itself, all I could think of was:</p>
  
  <pre><code>WHERE
  _TABLE_SUFFIX = FORMAT_DATE('%Y%m%d', DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY))
  </code></pre>
  
  <p>Which works great when running manually but obviously generates yesterday's date when I use backfill (rather than the backfill <code>run_date</code>)<br>
  I tried using <code>@run_date</code> w/ &amp; w/o offset but it's not a valid query.</p>