title: Update large set of documents without knowing _id
body: <p>I would like up update a large set of documents in Elasticsearch at once.
  One document looks like this:</p>
  
  <pre><code>{
    "_index": "vue_storefront_magento_1_1587559712",
    "_type": "product",
    "_id": "1123",
    "_version": 56,
    "_score": 7.7135754,
    "_source": {
      "sku": "381735",
      "score": "1"
    }            
    "fields": {
      "updated_at": [
        1589880769000
      ]
    },
    "highlight": {
      "type_id": [
        "@kibana-highlighted-field@configurable@/kibana-highlighted-field@"
      ],
      "sku": [
        "@kibana-highlighted-field@381735@/kibana-highlighted-field@"
      ]
    }
  }
  </code></pre>
  
  <p>I have a JSON file that contains the data I want to update, there is no _id field, only an SKU. I want to use this JSON to create the request to ElasticSearch to update.</p>
  
  <pre><code>[
    { "sku": 381735, "score": 2 },
    { "sku": 381736, "score": 3 },
    { "sku": 381737, "score": 4 }
  ]
  </code></pre>
  
  <p>I would like to update all of the score fields based on the SKU field in the _source.
  Is this possible? I already looked at the update by query API but can't figure it out :-/</p>