title: How to query by parent in ElasticSearch 6.5?
body: <p>I know we use <code>has_child</code> to get <strong>parent-child</strong> structure data, but <code>has_parent</code> can't query by parent field.
  I want to query by the parent so I must use <code>has_parent</code>, but then return data is parent data in <code>inner_hits</code>, how can I query by parent and structure data is like <code>has_child</code>?</p>
  
  <hr>
  
  <p><strong>Request body:</strong></p>
  
  <pre><code>{
  "query": {
      "has_parent": {
          "parent_type": "order",
          "query": {
              "bool":{
                  "should": [
                      {
                          "regexp": { "order_id": ".*100000156.*"}
                      },
                      {
                          "regexp": { "pro_id": ".*70LTJ315.*"}
                      }
                  ]
              }
          },
          "inner_hits": {"size": 10}
      }
  },
  </code></pre>
  
  <p>I want parent data in the <code>hits._source</code>, child data in the <code>inner_hits</code> and simultaneously query by parent field. I don't know how to do the same.</p>