title: Loki parse JSON and filter by field
body: <p>I'm logging a JSON which is being shown as a detected field <code>log</code> in Grafana:</p>
  <p><a href="https://i.stack.imgur.com/mtTJo.png" rel="nofollow noreferrer">Screenshot of detected fields</a></p>
  <p>Now I want to filter the logs by level name, but I can't figure out how...</p>
  <p>I thought something like this would work, but doesn't, no results are returned:</p>
  <p><code>{app=&quot;hello&quot;} | json | line_format &quot;{{.log}}&quot; | levelname=&quot;ERROR&quot;</code></p>
  <p>What am I missing?</p>