title: ElasticSearch _knn_search query on multiple fields
body: <p>I'm using ES 8.2. I'd like to use approximate method of <code>_knn_search</code> on more than 1 vector. Below I've attached my current code searching on a single vector. So far as I've read <code>_knn_search</code> does not support search on <code>nested</code> fields.
  Alternatively, I can use multi index search. One index, one vector, one search, sum up all results together. However, I need to store all these vectors together in one index as I need also to perform filtration on some other fields besides vectors for knn search.</p>
  <p>Thus, the question is if there is a work around how I can perform <code>_knn_search</code> on more than 1 vector?</p>
  <pre><code>search_vector = np.zeros(512).tolist()
  es_query = {
          &quot;knn&quot;: {
              &quot;field&quot;: &quot;feature_vector_1.vector&quot;,
              &quot;query_vector&quot;: search_vector,
              &quot;k&quot;: 100,
              &quot;num_candidates&quot;: 1000
          },
          &quot;filter&quot;: [
              {
                  &quot;range&quot;: {
                      &quot;feature_vector_1.match_prc&quot;: {
                          &quot;gt&quot;: 10
                      }
                  }
              }
          ],
      &quot;_source&quot;: {
          &quot;excludes&quot;: [&quot;feature_vector_1.vector&quot;, &quot;feature_vector_2.vector&quot;]
      }
      }
  </code></pre>