title: How to set up elasticsearch routing on existing index?
body: <p>I have an index which uses the default routing of elasticsearch. Now I want to set up my own routing, how do I implement this?</p>
  
  <p>The example in the <a href="https://www.elastic.co/blog/customizing-your-document-routing" rel="nofollow">official doc</a> is:</p>
  
  <pre><code>$ curl -XPUT 'http://localhost:9200/store/order/_mapping' -d '
  {
     "order":{
        "_routing":{
           "required":true,
           "path":"customerID"
        }
     }
  }
  </code></pre>
  
  <p>After doing this, do I need to reindex of even rebuild the whole index?</p>