title: Logstash/ElasticSearch - How to deal with parent/child relationship
body: <p>I have added a mapping in my elastic search index in order to have a child for my documents:</p>
  
  <pre><code>PUT /test/_mapping/goals
  {
    "goals": {
          "_all": {
             "enabled": false
          },
          "_parent": {
             "type": "myparentdoc"
          },
          "_routing": {
             "required": true,
             "path": "_id"
          },
          "properties": {
             "goals": {
                "type": "long",
                "null_value": 0
             }
          }
       }
    }
  </code></pre>
  
  <p>Now I would like to import the corresponding documents with logstash.</p>
  
  <p>How can I configure my logstash in order to give the parent id information.</p>
  
  <p>I tried to configure <em>action</em> parameter in <em>elasticsearch</em> output configuration without any success (based on elasticsearch documentation for bulk processing of children docs).</p>
  
  <p>To summarize, how should I put <em>_parent</em> information? </p>
  
  <p>Any idea? </p>
  
  <p>Thanks</p>