title: Firebase first_open count becoming less
body: <p>Yesterday, when I ran the query,</p>
  <pre><code>SELECT
    Count(*)
  FROM 
    `analytics_xxx.events_*`
   
  WHERE 
    event_name = 'first_open'
  </code></pre>
  <p>It return 571 but today when I ran the same query it was 560. How come the count become less in one day. Is Firebase deleting the <code>first_open</code> event from the database?</p>