title: Include joined children with Elasticsearch GET request
body: <p>I have an Elasticsearch index <code>events</code> that has a join field so that an event can have multiple instances (i.e. the same event can occur on different dates). In this simplified mapping, an <code>event</code> doc has fields for <code>title</code> and <code>url</code> while an <code>instance</code> doc has start/end date fields:</p>
  <pre class="lang-json prettyprint-override"><code>{
    &quot;mappings&quot;: {
      &quot;properties&quot;: {
        &quot;title&quot;: {
          &quot;type&quot;: &quot;text&quot;
        },
        &quot;url&quot;: {
          &quot;type&quot;: &quot;keyword&quot;
        },
        &quot;dt&quot;: {
          &quot;type&quot;: &quot;date&quot;
        },
        &quot;end_dt&quot;: {
          &quot;type&quot;: &quot;date&quot;
        },
        &quot;event_or_instance&quot;: {
          &quot;type&quot;: &quot;join&quot;,
          &quot;eager_global_ordinals&quot;: true,
          &quot;relations&quot;: {
            &quot;event&quot;: &quot;instance&quot;
          }
        }
      }
    }
  }
  
  </code></pre>
  <p>I know how to get an <code>event</code> and includes all of its instances using <code>has_child</code>:</p>
  <pre class="lang-json prettyprint-override"><code>GET /events/_search
  {
    &quot;query&quot; : {
      &quot;bool&quot;: {
        &quot;filter&quot;: [
          {
            &quot;term&quot;: {
              &quot;_id&quot;: {
                &quot;value&quot;: &quot;c8871a79-1907-46c0-958c-9731c529b93e&quot;
              }
            }
          },
          {
            &quot;has_child&quot; : {
              &quot;type&quot; : &quot;instance&quot;,
              &quot;query&quot; : { &quot;match_all&quot;: {} },
              &quot;inner_hits&quot; : {
                &quot;_source&quot;: true,
                &quot;sort&quot;: [{&quot;dt&quot;: &quot;asc&quot;}]
              }
            }
          }
        ]
      }
    },
    &quot;_source&quot;: true
  }
  </code></pre>
  <p>This works fine, but is there a way to do this using the Get/Multi-get API instead of the Search API?</p>