title: Kibana querying for string length
body: <p>Is there a way to query for a value of a certain length in Kibana?</p>
  
  <p>For example, given the following two KV pairs:</p>
  
  <pre><code>key: "some"
  key: "something"
  </code></pre>
  
  <p>I would like to search for key.length > 5 and retrieve "something" only. </p>
  
  <p>The other option I see is to add a tag from logstash, but then I'll have to reload a couple hundred GB. </p>