title: how to search in n element elastic-search-dsl
body: <p>I've a problem in elastic search to know if an element already exist, because for a lot of practical reason I store in elastic-search meta data of image for each user (the author) and to avoid some attack I need to be sure that the image hasn't be already saved. here is a standard json file :                                                                                 </p>
  
  <pre><code>{
  "user_group": "user",
  "user_data": {
      "name": "myname"
  },
  "user_image": [
      {
          "size": "1920x1080",
          "location": "my_city",
          "description": "my_desc",
          "name": "myname",
          "md5_checksum_image": "a_md5"
      },
      {
          "size": "1920x1080",
          "location": "my_city",
          "description": "my_desc",
          "name": "myothername",
          "md5_checksum_image": "a_md5"
      }
    ]
  }
  </code></pre>
  
  <p>my problem is that I could have thousand of image so ho could I test with a query if I've already registered this image by looking at the checksum ? </p>