title: Selecting InfluxDB records with non-empty tags gets terribly slow
body: <p>I'm running Influx v1.3. I have a measurement with ~2+ million records within 1 month timespan and 10 tags within. Out of those, I'm interested in <code>user_id</code> and <code>article_id</code>. </p>
  
  <p>I'm trying to extract number of events logged for specific <code>user_id</code> with non-empty <code>article_id</code>.</p>
  
  <p>The query for selecting all user's events is blazingly fast:</p>
  
  <pre><code>select count(*) from pageviews where user_id = '92363';
  </code></pre>
  
  <p>The query for specific event for user and article is blazingly fast:</p>
  
  <pre><code>select * from pageviews where user_id = '92363' and article_id = '879729';
  </code></pre>
  
  <p>But when I try to add filter for non-empty (or empty) <code>article_id</code>, the query runs for tens of seconds.</p>
  
  <pre><code>select count(*) from pageviews where user_id = '92363' and article_id != '';
  select count(*) from pageviews where user_id = '92363' and article_id !~ /.*/;
  </code></pre>
  
  <p>Is there something I'm doing wrong or something I should configure within the database? This doesn't seem to be right. The number of user's events is &lt;100, I'd literally went through them faster manually.</p>
  
  <p>I'm currently running the default configuration.</p>
  
  <p>Thanks.</p>