title: Elasticsearch: Async "delete by query" and index
body: <p>I'm using <a href="https://www.elastic.co/guide/en/elasticsearch/plugins/current/delete-by-query-usage.html" rel="nofollow">delete by query</a> plugins for elastic search.</p>
  
  <p>I have a index products with a integer field size. I want delete all document with size 10. I have over 5000 documents with size 10. </p>
  
  <p>If i try:</p>
  
  <pre><code>DELETE /products/product/_query?q=size:10
  </code></pre>
  
  <p>this query requires over 2 minutes (delete by query is really slow), if i post a new <code>product</code> with size 10 during deleting, eg.:</p>
  
  <pre><code>POST /products/product/
  {
      "size": 10
  }
  </code></pre>
  
  <p>what happens?</p>
  
  <p>my new <code>product</code> is saved or deleted?</p>